Kategori: Statistics Education

  • Social Media Polls vs. Random Surveys: Understanding Selection Bias Before Making Decisions

    In recent years, I have increasingly heard remarks like this in meetings: “We ran an Instagram poll yesterday, and 80% of our followers agreed.” Or: “Our customer WhatsApp group says they love the new product.” Such polls are quick, inexpensive, and feel inherently democratic. Anyone is welcome to participate.

    That, however, is precisely where the trouble begins. Because anyone can participate, you never truly know who actually responded. And in survey research, who answers is almost always far more critical than how many answered.

    This article examines the fundamental distinction between social media polls and random probability surveys, highlights a famous historical lesson, and provides a practical framework for choosing the right methodology for your decisions.

    The Core Difference: Who Selects the Respondents

    In a social media poll, respondents select themselves. Only individuals who happen to see the post, feel engaged by the topic, and are willing to spend the time will respond. In research methodology, this is called a self-selected sample.

    A few defining characteristics of self-selected samples deserve close attention:

    • Coverage is restricted to followers. An account’s followers do not represent the general population. They tend to share similar interests, demographics, or viewpoints with the account owner.
    • Stronger opinions are overrepresented. People with intense enthusiasm or vehement disapproval are far more motivated to participate than those with moderate views.
    • Algorithms shape visibility. Who sees the post is governed by platform algorithms, not the researcher’s design.
    • A single individual can vote repeatedly across multiple accounts or devices.

    In a random probability survey, the researcher selects respondents using probabilistic procedures. Every member of the defined population has a known, non-zero chance of selection. Because that probability is known, researchers can mathematically calculate how far the sample estimate might deviate from the true population value—what we call the margin of error.

    Why Big Numbers Cannot Rescue a Biased Sample

    Many assume that a poll with 10,000 votes must be more reliable than a survey of 400 respondents. The intuition seems straightforward: larger numbers must mean greater representation.

    That reasoning holds true only for random probability samples. Increasing sample size reduces random sampling error. But if the selection mechanism itself is biased, collecting more responses does not reduce systematic error (bias). It merely produces an inaccurate estimate with greater statistical confidence.

    A simple analogy illustrates this: if your bathroom scale is miscalibrated by 2 kilograms, stepping on it a hundred times will not make the weight reading any more accurate. The average remains 2 kilograms off; you are simply more confident in the wrong number.

    A Historical Lesson: The 1936 Literary Digest Poll

    The most renowned cautionary tale in survey history unfolded during the 1936 United States presidential election. The Literary Digest, a wildly popular magazine at the time, mailed millions of mock ballots to its subscribers and to individuals listed in telephone directories and automobile registries. Over two million ballots were returned.

    Based on this massive response, the Literary Digest confidently projected that Alf Landon would defeat incumbent Franklin D. Roosevelt by a decisive margin. The actual election yielded the exact opposite: Roosevelt secured a historic landslide victory.

    What went wrong? Analysts later highlighted two fatal flaws. First, the contact lists drew disproportionately from affluent households during the height of the Great Depression. Second, those who returned the postcards were not a random cross-section of recipients, introducing severe nonresponse bias. In the very same election cycle, pioneering pollsters using vastly smaller samples—selected through disciplined quota and probability sampling—correctly predicted Roosevelt’s triumph.

    The lesson has endured for nearly a century: bigger is not synonymous with better.

    Margin of Error: What Can and Cannot Be Calculated

    For a simple random sample, the margin of error for a proportion at a 95% confidence level can be calculated using standard formulas. Under the most conservative assumption (a 50% proportion) in a large population, the numbers look like this:

    Random Sample SizeMargin of Error (95% Confidence)
    100approximately ±9.8%
    400approximately ±4.9%
    1,068approximately ±3.0%
    2,401approximately ±2.0%
    Self-selected poll, regardless of sizecannot be meaningfully calculated

    Two observations stand out. First, cutting the margin in half (from roughly ±5% to ±2.5%) requires roughly four times the sample size. Precision comes at a real cost. Second, self-selected polls have no mathematically valid margin of error because there is no underlying probability mechanism.

    A vital caveat: margin of error only captures sampling error. Even random surveys encounter non-sampling errors, such as incomplete sampling frames, non-response attrition, and leading question wording. A sound survey is never completely free of error, but it understands where vulnerabilities lie and systematically works to minimize them.

    Are Social Media Polls Useless?

    Not at all. Social media polls remain useful for specific, targeted purposes:

    • Taking the pulse of your own audience, such as learning which content themes your followers prefer.
    • Sparking community engagement and discussion.
    • Generating exploratory hypotheses prior to investing in formal research.

    The misstep occurs when organizations use casual poll results to declare what “the broader public” or “the market” demands, and then make significant capital or strategic bets based on those claims.

    A Decision Framework for Choosing Your Method

    Before deciding between an informal poll and a formal survey, ask yourself three core questions:

    1. Whose opinion am I truly trying to measure? If the answer is “the people following my account,” a quick poll suffices. If the answer is “consumers across Metro Jakarta” or “all employees nationwide,” you require a representative sample.
    2. What is the magnitude of the decision? For small, easily reversible choices, rough directional feedback is often adequate. For product launches, capital investments, or organizational policy, you need defensible data.
    3. Do I need to know how certain the findings are? If yes, only probability-based sampling can provide measurable statistical bounds.

    What About Online Surveys?

    A common follow-up question is whether all online surveys suffer from the same weaknesses as social media polls. The answer is no. Online surveys can be methodologically rigorous—for instance, by sending survey invitations exclusively to randomly sampled customer or employee lists, utilizing verified probability-recruited research panels, or applying post-stratification weighting to align sample demographics with population parameters.

    What matters is not the medium—digital versus face-to-face—but the underlying respondent selection procedure. An online survey sent to a random sample of an employee roster is vastly more trustworthy than an intercept survey conducted on a street corner where interviewers pick respondents at convenience.

    Closing Thoughts

    In today’s digital landscape, collecting thousands of responses takes just a few clicks. Yet because collecting data has become so effortless, critical thinking is more essential than ever. Thousands of self-selected responses can easily be far less accurate than a few hundred properly sampled ones.

    Before trusting any survey finding, the most valuable question to ask remains unchanged: how were the respondents selected?

    Read also: planning a customer survey, brand research, or market study with rigorous, representative sampling? Explore our Market Research & Survey Services.


    Looking to design rigorous surveys, run representative market research, or train your team in sampling methodology? The datalytics.indo team provides end-to-end research services: business question formulation, questionnaire design, sampling strategy, data processing, statistical analysis, and board-ready reporting. We also deliver hands-on in-house training in survey design and applied statistics. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

    WhatsApp: +62 811 889 757 · Instagram: @datalytics.indo

    Margin of error calculated using simple random sampling formula, 50% proportion, 95% confidence level, and large population.

    #surveys #marketresearch #sampling #methodology #datalyticsindo

  • Ask a Statistician: 3 Questions I Get Asked the Most (and My Honest Answers)

    Every time I run a training session or supervise a thesis, the same three questions come up. The wording varies, but the core is identical. This Saturday, I’m answering all three in one place, in language you can use right away.

    The questions: how large a sample is enough, does non-normal data require a non-parametric test, and does a non-significant result mean your research failed. Let’s start with the one I hear most often.

    Question 1: “How large a sample is enough?”

    My honest answer: it depends on what you want the sample to tell you. There is no magic number.

    If your goal is estimating a proportion (for example, “what percentage of customers are satisfied?”), sample size determines precision, measured by the margin of error. At a 95% confidence level and the most conservative assumption (proportion of 50%), the required random sample is roughly:

    Margin of errorRandom sample needed
    ±10%about 97 people
    ±5%about 385 people
    ±3%about 1,068 people
    ±2%about 2,401 people

    Notice the pattern: to cut the margin from ±5% to ±2.5%, you don’t just double the sample—you need roughly four times as many respondents. That’s why tight precision is expensive.

    Two important caveats. First, these numbers assume a random sample. A convenience sample of 10,000 from a group chat poll isn’t automatically more accurate than 400 randomly selected respondents, because what randomization guarantees is the ability to quantify the error, not the sheer count. Second, for small populations the requirement drops. With a finite-population correction, a population of 2,000 with a ±5% margin needs only about 323 respondents, and a population of 500 about 218.

    If your goal isn’t estimating a proportion but testing relationships or building a model (regression, SEM, PLS-SEM), the logic changes: what matters is statistical power, the number of variables or paths in the model, and the effect size you want to detect. So don’t copy “100 respondents” from someone else’s thesis without checking whether their objective matches yours.

    Question 2: “My data isn’t normal. I have to use a non-parametric test, right?”

    This is the question that sends students into a panic two weeks before their defense. My short answer: not necessarily, and you may be testing normality on the wrong thing.

    In many analyses—regression in particular—the normality assumption applies to the residuals (the difference between observed and predicted values), not to each raw variable individually. Raw variables can be skewed, yet the residuals may still satisfy the assumption.

    A few things to check before switching to a non-parametric test:

    • What does your chosen test actually assume? The t-test and ANOVA, for instance, require normality within each group or of the residuals, and both are reasonably robust against mild violations when the sample isn’t tiny.
    • Look at the visuals. Histograms and Q-Q plots are often more informative than a single p-value from a normality test. Formal tests like Shapiro-Wilk can “reject” normality in large samples due to deviations that are practically trivial.
    • Know your alternatives. If the assumption truly fails, non-parametric tests aren’t the only option. You can also transform the data or use methods that are robust to violations.

    The wording in your results section matters too. Instead of writing “the data were not normal so a non-parametric test was used,” examiners appreciate a sentence that states which assumption was tested, with which tool, on which object, and what the consequence was.

    Question 3: “My result isn’t significant. Does that mean my research failed?”

    No. And this is probably the most damaging misconception in research.

    A p-value answers a narrow question: if there really were no effect, how rarely would I see data as extreme as this? It does not answer “is the effect important,” and a large p is not evidence that the effect doesn’t exist. It could simply mean your sample was too small to detect it.

    Imagine a training program that raises the average competency score by 2 points on a scale with a standard deviation of 10 (a small effect). Tested on 30 people, that effect will almost certainly go undetected, and you might conclude “the training had no impact.” Tested on 3,000 people, the exact same effect produces a tiny p-value and you conclude “significant impact.” The effect is still two points. Only the sample size changed.

    That’s why I recommend the following when reporting results:

    1. Report the effect size (e.g., the coefficient or the mean difference), not just p.
    2. Include a confidence interval so readers can see the plausible range.
    3. Discuss the sample’s power to detect the effect, especially when the result is non-significant.
    4. Ask about practical relevance: does a difference that size matter for decisions or costs?

    A non-significant result, reported honestly, is a legitimate finding. What’s dangerous is the habit of trying different analyses until something is significant, then reporting only that one.

    Bonus: three sentences you can adapt for your methods and results sections

    Sometimes what trips students up isn’t the analysis but the writing. Here are template sentences you can tailor to your own case. Fill in the numbers with your own data and decisions.

    On sample size: “The sample size was determined to achieve a maximum margin of error of ±5% at a 95% confidence level, requiring at least approximately 385 respondents for a large population. The sample was selected using [state the sampling technique].”

    On assumptions: “The normality assumption was assessed on the model residuals using a Q-Q plot and the [state the test], and the results [met or did not meet the assumption]. Accordingly, the analysis proceeded with [state the method].”

    On a non-significant result: “The effect of [variable A] on [variable B] was not statistically significant (coefficient [value]; 95% confidence interval [lower] to [upper]). With a sample size of [n], this study had limited power to detect a small effect, so this result should be interpreted as [an honest interpretation] rather than as evidence of no effect.”

    Note that all three sentences state the reason, not just the decision. That’s what examiners look for: proof that you know why you did something.

    The common thread

    All three answers share one principle: don’t apply rules of thumb without understanding the rationale behind them. Sample-size thresholds, normality tests, and the p < 0.05 cutoff are all tools. Tools used without understanding their purpose produce conclusions that look neat but are hard to defend in a thesis defense or a boardroom.

    If you have another question, leave it in the comments or send a direct message. Good questions will be featured in the next Saturday edition.

    Read also: [Data Analysis & Statistical Services](https://datalyticsindo.com/en/data-analysis-statistical-services/) – statistical analysis, data processing, and methodology support from the Datalytics team.


    Not sure how to determine your sample size, choose the right test, or interpret your analysis results for your thesis, dissertation, or workplace report? The datalytics.indo team helps with research design and sampling, instrument validation, analysis (regression, PLS-SEM/SEM, path analysis, factor analysis, cluster analysis, and more), all the way to interpretation. Private coaching in SPSS and SmartPLS is also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

    WhatsApp: 0811889757 · Instagram: @datalytics.indo

    #statistics #sampling #pvalue #thesis #datalyticsindo

  • 4,149 Environmental Crime Incidents, 32% in One Province: Does That Mean North Sumatra Is the “Most Damaged”?

    When you picture crime, what usually comes to mind is theft, fraud, or violence. Few people immediately think of forests cleared without permits, fish poached from the sea, or mines operating outside the law. Yet crimes against the environment cause enormous damage, and their victims include not just people living today, but future generations as well.

    The 2024/2025 Crime Statistics from BPS (Statistics Indonesia) include a dedicated section on this category of crime. Inside it, one figure stands out prominently: North Sumatra Regional Police recorded 1,334 incidents, roughly 32% of all environmental crimes in Indonesia. Let’s examine that number carefully.

    What counts as an environmental crime?

    BPS groups five types into this category:

    1. Forest destruction prevention and suppression offences (illegal logging)
    2. Plantation offences
    3. Fisheries offences (illegal fishing)
    4. Mineral and coal mining offences (illegal mining)
    5. Oil and gas offences

    The figures for 2024 compared to 2023:

    Type20232024Trend
    Plantation offences1,1601,459Up
    Oil and gas offences1,0321,249Up
    Mining (illegal mining)839796Down
    Forest destruction (illegal logging)560446Down
    Fisheries (illegal fishing)244199Down
    Total3,8354,149Up

    The two types that increased—plantation and oil and gas offences—account for approximately 65% of all environmental crimes in 2024. Both also saw substantial growth compared to the prior year: plantation offences climbed about 26%, while oil and gas rose around 21%.

    An uneven geographic distribution

    The three regional police commands (Polda) with the highest incident counts:

    • North Sumatra: 1,334 (about 32% of the national total)
    • South Sumatra: 230
    • East Java: 212

    And those with the lowest:

    • West Sulawesi: 1
    • Papua: 11
    • North Maluku: 19

    The gap between North Sumatra and the second-ranked province is more than fivefold. Meanwhile, Papua, known for its vast rainforests and natural resources, recorded only 11 incidents.

    The critical question: what does this number actually measure?

    This is where critical thinking is essential. The question is not “where is environmental destruction greatest?”, but rather “where are environmental crimes most actively recorded and prosecuted?” Those are two completely different things.

    First, these are crimes without reporting victims. Like narcotics, environmental crimes are rarely reported by individual victims. The victims are ecosystems, the broader public, or future generations. For a case to be recorded, law enforcement or inspectors must actively discover it, investigate, and take action. The recorded case count reflects enforcement and surveillance capacity, not simply the true underlying number of violations.

    Second, an extremely low figure does not automatically mean a pristine area. Recording 1 incident in West Sulawesi or 11 in Papua could mean violations are genuinely rare. But it could also reflect limited surveillance across vast, rugged terrain with few enforcement personnel available. In such contexts, “unrecorded” is not the same as “non-existent.”

    Third, a high figure can indicate active enforcement. A province with elevated numbers may indeed have more violations. But it may also have a police force that is particularly active in investigating and cracking down, bringing more cases to light. In certain settings, a rising number signals improving enforcement rather than deteriorating environmental conditions.

    Fourth, the local economic structure shapes the types of offences. Plantation hubs will naturally record more plantation offences. Oil-producing regions will log more oil and gas offences. Regional disparities largely mirror differences in economic geography, not the moral character of residents.

    The takeaway: enforcement statistics measure institutional activity

    This is perhaps the most important lesson from this dataset, and it applies equally to narcotics, corruption, and many other crimes: police registration data for crimes without individual reporting victims measure law enforcement activity, not the true scale of the underlying problem. Using them to declare “Province X is the most degraded” or “Province Y is the cleanest” is a leap unsupported by data.

    To measure actual environmental damage, we need different data sources: satellite imagery on forest cover change, licensing databases, field surveys, ecological loss assessments, and environmental quality metrics. Criminal statistics fill only one piece of the puzzle.

    What can researchers explore further?

    For researchers and students, several questions are worth exploring:

    • Is there a relationship between recorded case counts and enforcement resources across regions (investigators, budgets, territorial reach)?
    • How do environmental crime statistics correlate with remote sensing data on land cover change?
    • Why did plantation and oil and gas offences rise while others declined? Were there regulatory shifts, commodity price changes, or specific operations?
    • How do recorded environmental cases progress through prosecution, sentencing, and environmental remediation? Initial police statistics tell only the opening chapter of the legal process.

    Each question demands additional data and a far more rigorous approach than simply contrasting headline totals across provinces.

    Concluding thoughts

    Environmental crime demands that we look beyond headline statistics. Data remains essential, provided we are candid about what it measures. The figure of 4,149 is not a balance sheet of environmental degradation in Indonesia. It is a record of cases that made it into the formal enforcement system. What remains unrecorded—and what has been degraded without documentation—may well be vastly larger.

    Combining enforcement data with environmental indicators

    To evaluate environmental crime comprehensively, enforcement statistics must be paired with independent environmental metrics. Remote sensing (satellite imagery) can track changes in canopy cover or illegal mining footprints. Concession and licensing registers document lawful activities. Water, air, and soil quality monitoring reveal real-world impact. Natural resource revenues show economic stakes. Laying these layers together allows us to ask a far more meaningful question: which areas show significant environmental disturbance yet report virtually no legal cases? That gap is where true surveillance deficiencies lie.

    Community-based prevention

    Law enforcement alone is rarely sufficient. Evidence from many regions indicates that environmental crimes are prevented most effectively when surrounding communities have a tangible stake in safeguarding resources—such as through community forestry, small-scale fisheries co-management, or secure whistleblowing channels that guarantee follow-up. Crime statistics capture these outcomes in an ironic way: recorded complaints may initially surge as community trust improves, signaling that the oversight system has finally begun to work.

    Research ideas for students

    Compelling research topics include: examining the link between provincial police enforcement capacity and recorded environmental case volumes; comparative analysis of environmental offence categories mapped to regional economic structure; or qualitative case studies examining how provinces with high reporting rates developed their specialized investigation units. Each pairs empirical rigor with institutional insight.

    Quick Q&A

    Why is the total number of environmental crimes relatively small compared to other offences? Partly because these offences are less frequently detected through citizen reports, and enforcement requires specialized resources (technical investigators, expert witnesses, formal damage assessments). Investigations are also technically complex and lengthy, meaning cases often take more than one reporting cycle to conclude.

    Does a rising number mean environmental destruction is accelerating? Not necessarily. It can indicate strengthened enforcement and proactive inspections. This is why environmental crime records must always be interpreted alongside independent environmental condition indicators.

    Read also: Data analysis and statistical services


    Researching environmental governance, natural resource policy, or green criminology using secondary datasets? The datalytics.indo team supports students, researchers, and institutions from study design and secondary data processing through statistical modeling (regression, PLS-SEM/SEM, path analysis, factor and cluster analysis) to interpretation and publication. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • Mass Brawls Rose from 1.85% to 2.41% of Villages, and DKI Jakarta Is Highest: Read Regional Percentages with Care

    One of the most interesting parts of Indonesia’s Criminal Statistics 2024/2025 does not come from police records or victimization surveys. It comes from the Village Potential Census (Podes), a BPS data collection that treats every village and urban ward (desa/kelurahan) as a unit of observation. It includes a question about mass brawls in the past year.

    The result grabs attention: the share of villages and wards that experienced a mass brawl rose from 1.85% in 2021 to 2.41% in 2024. And the province with the highest share is… DKI Jakarta, at 18.73%.

    Before jumping to the conclusion that Jakarta is the “most brawl-prone province”, let us read the numbers calmly. This is where statistical thinking helps us avoid rushing to conclusions.

    What does Podes actually count?

    Podes does not count the number of brawls. It counts the percentage of villages and wards that experienced at least one incident in the past year. So a ward with ten incidents and a ward with one incident are both counted as “experienced”. The indicator measures the spread of conflict, not its intensity.

    The recorded types of mass brawl include several forms: fights between resident groups, between residents of different villages, clashes between residents and security forces, between residents and government officials, fights between students, and inter-ethnic conflict. In 2024 the most common type was fights between resident groups, which rose slightly from 1.00% (2021) to 1.09% (2024). BPS lists common causes such as insults, misunderstandings, juvenile delinquency, and old grudges.

    National trend: up, but from a small base

    The rise from 1.85% to 2.41% is a relative increase of about 30%. In absolute terms it is only about 0.56 percentage points. Both views are correct, and both should be stated together. Saying “up 30%” without context sounds frightening. Saying “only half a point” may downplay it. It is better to give both.

    BPS interprets this as social conflict potential in the form of mass brawls still being fairly high and tending to spread to more areas, and names several possible factors: rising mobility, tension between residents, economic pressure, and local conflict resolution mechanisms that are not yet optimal. That is a reasonable explanation, but note that this data does not test causes. It only describes a pattern.

    The reassuring side: most conflicts are settled peacefully. In 2024, 94.29% of incidents were resolved peacefully (down from 95.49% in 2021), and about 5.71% remained unresolved. Even a small decline deserves attention because it signals challenges in village-level resolution mechanisms.

    Variation across provinces

    The three provinces with the highest percentages in 2024:

    ProvinceVillages/wards that experienced a mass brawl
    DKI Jakarta18.73%
    Maluku11.41%
    North Maluku11.33%

    And the lowest: Riau Islands (0%), South Kalimantan (0.20%), and North Kalimantan (0.41%). The gap between DKI Jakarta and the national average (2.41%) is almost eightfold. BPS says the difference reflects inequality in the intensity and frequency of mass conflict across regions, and points to socio-economic, cultural, and community interaction patterns as possible causes.

    The statistical trap: areal units that are not comparable

    This is where care is needed. The indicator is computed per village or ward. But villages and wards are not uniform in size. A ward in DKI Jakarta is typically densely populated with a small area. A village in Kalimantan or Papua may have few residents spread over a large area. In a small, dense ward, the chance of at least one incident in a year is naturally higher, because many people interact in a tight space. With smaller and denser units, the percentage of “wards that experienced an incident” tends to be higher even if the number of incidents per resident is not.

    In statistics this relates to the modifiable areal unit problem: results can change depending on how we divide regions into units of analysis. The percentage of villages is not the same as incidents per 100,000 residents. They answer different questions.

    So 18.73% for Jakarta does not automatically mean Jakarta residents are involved in mass brawls more often than residents of other provinces. What we can safely say: in Jakarta, the proportion of areal units (wards) that experienced at least one mass brawl in a year is the highest. To conclude more, we need measures adjusted for population and more detailed incident data.

    What can we learn from a criminology perspective?

    Mass brawls are interesting to study because they do not fit neatly into the “offender and victim” framework of, say, theft. They are collective crime, often rooted in community tension, identity, and rivalry. Some relevant theories: social disorganization theory (weak cohesion and informal control in dense neighborhoods with high turnover), strain theory (economic pressure driving frustration), and communal conflict approaches. The strength of peaceful resolution at village level (94.29%) also reminds us that local social capital, such as community leaders, resident mediation, and customary law, is an asset often neglected in security policy.

    Three notes for readers of this kind of data

    1. Separate spread from intensity. The percentage of areas with an incident is not the number of incidents.
    2. Beware of areal units that are not comparable. Compare areas of similar size, or use per-capita measures.
    3. Do not infer causes from patterns. Descriptive data points to where, not why.

    Two interesting research designs

    Podes data opens several research possibilities. The first is a multilevel model: villages and wards are nested within districts, regencies, and provinces. We can test village-level factors (density, inequality, facilities, neighborhood security activities) alongside broader regional factors, without violating independence assumptions. The second is spatial analysis: do mass brawl incidents cluster geographically? Techniques such as Moran’s I or spatial cluster analysis can show whether there are “hot spots” that cross administrative boundaries, so prevention policy can be designed across regions.

    The role of early detection and mediation

    BPS highlights the importance of strengthening village officials, community leaders, and community institutions in early detection and mediation. The fact that about 94% of conflicts end peacefully at the local level shows that this capacity already exists. A smart policy would strengthen the mechanisms already working, for example mediation training for village officials and communication forums between youth groups, rather than replacing them with a purely repressive approach. For fights between students, schools and families play an important role that police statistics do not capture.

    Quick Q&A

    Is a mass brawl the same as student brawling? Student brawls are one form. In the Podes classification, mass brawls also include fights between resident groups, between villages, clashes with security forces, and inter-ethnic conflict. Because the scope is wide, interpretation by type is more meaningful than the combined figure.

    Is the rise from 1.85% to 2.41% alarming? It is a rise worth monitoring, but the base figure is still small and most cases are settled peacefully. A more useful question is whether the trend continues in the next census, and which regions show the sharpest increases.

    Read also: [Data analysis and statistical services](https://datalyticsindo.com/en/data-analysis-statistical-services/)


    Researching social conflict, community cohesion, or security policy with Podes data and other secondary data? The datalytics.indo team helps students, lecturers, and institutions: research design, data processing, statistical analysis (regression, PLS-SEM/SEM, path analysis, factor, cluster, and more), through to interpretation and publication. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • Quick Count Is Not a Prediction: How It Works, and 5 Reasons It Sometimes Misses

    Every time there is a general election or a local election, two things almost always happen. First, a polling firm announces its quick count a few hours after voting closes. Second, someone unhappy with the result says, “Quick count is a lie!” or, if the result suits them, “Quick count proved to be accurate!”

    I have worked on political surveys and quick counts for several local elections, and one thing I always say: a quick count is not a prediction, not magic, and not just a number you can either trust blindly or dismiss as fake. It is a statistical method, and like any statistical method it has conditions for working well and limits we need to understand.

    How does a quick count work?

    The idea is simple. Instead of waiting for the official tally from every polling station (TPS), which number in the hundreds of thousands nationwide, we draw a random, measured sample of polling stations. A field officer at each selected station photographs or records the result announced there (the official count form) and sends it to a data center. From that sample we estimate the result for the whole population of polling stations, together with a margin of error.

    Notice the difference from an ordinary opinion survey. An opinion survey asks people about their choice or intention. A quick count records the actual result at the polling station, so it does not depend on respondents’ honesty or memory. That is why a well-designed and well-run quick count is usually very accurate, often within one percentage point of the official result.

    It also differs from an exit poll, which interviews voters as they leave the polling station. An exit poll still relies on what voters say (and some prefer not to tell the truth), while a quick count reads the official numbers at the station.

    Why can a small sample be so accurate?

    Because inferential statistics is built for exactly that. If the sample is random and large enough, the sample estimate lands close to the population value, with an error we can calculate. Think of tasting a pot of soup: one spoonful, properly stirred, is enough to know the whole pot. In a quick count, the “stirring” is the random selection of stations, usually with stratification (for example by region) so that every group is represented.

    Five reasons a quick count can miss

    A quick count can be spot on, but sometimes it is not. These are the most common causes.

    1. A sample of stations that is not truly random

    If stations are chosen because they are “easy to reach” or because a field officer happens to be available there, the sample is biased toward places that are easy to access (usually urban areas and main roads). The result leans toward the voting pattern of those areas. A documented random selection is the most basic requirement.

    2. An outdated sampling frame

    The list of stations used for selection must match reality on election day. If stations were merged, split, or moved, or the list is simply old, some areas have no chance of being selected, and the sample no longer represents the real population.

    3. Incoming data that is incomplete and unbalanced

    Data from stations does not arrive all at once. Urban stations with good signal usually report first, while remote stations report later. If an organization announces results too early, when only part of the data is in and it is dominated by certain areas, the estimate can lean the wrong way. That is why professional firms wait until the data is large and balanced enough before releasing.

    4. A very thin margin

    This is not an error but a natural limit of the method. If candidate A gets 50.3% and candidate B 49.7%, the gap is 0.6 points. A quick count’s margin of error is typically around one percentage point or more. In that situation, a quick count cannot declare a winner with high confidence. An honest firm will say the result is “still within the margin of error”. A firm that insists on naming a winner is acting beyond the limits of its statistics.

    5. Transmission and data entry errors

    A blurry photo of a form, a misread number, or a typo are operational risks. Layered verification, including consistency checks (for example, valid plus invalid votes must match the total number of voters present), helps catch these errors before they damage the estimate.

    The margin of error is part of the result

    The most common mistake in quick count reporting: the result is written as a single number, and the margin of error is forgotten or buried in a footnote. A properly stated quick count result looks like this:

    > Candidate A: 54.2% (±1.0%). Candidate B: 45.8% (±1.0%).

    This means that, with 95% confidence, candidate A’s true value lies between roughly 53.2% and 55.2%. It is clear that A leads, because A’s lower bound (53.2%) is far above B’s upper bound (46.8%). But if the result is 50.4% (±1.0%) versus 49.6% (±1.0%), the ranges overlap, and the honest conclusion is “cannot be determined yet”.

    What makes a quick count trustworthy?

    A few signs you can check yourself as a reader:

    • The methodology is open: sample size, sampling method, margin of error, and confidence level are stated.
    • The sample is documented and can be inspected, not just “we took 2,000 polling stations”.
    • The data source is clear: official results at the polling station, not perceptions.
    • The organization is transparent about its funding and affiliations.
    • It does not force a conclusion when the gap is within the margin of error.
    • It states differences from the official result, including when they exist, and explains why.

    How quick count relates to the official count

    One point needs clarifying: a quick count is not a replacement for the official count by the election authority. It serves as an independent verification tool and as early information for the public. If the quick count and the official result differ greatly, the question should go in two directions: is there a weakness in the quick count methodology, or a problem in the official counting process? Accusing one side without checking the data is equally unscientific.

    Lessons that apply beyond elections

    The thinking behind a quick count applies to any survey: random sampling, an up-to-date frame, complete data, and honesty about uncertainty. That is why I always say elections are simply the most visible stage for the same statistical principles you use in your thesis or customer survey.

    Why tight precision needs a big sample

    In a simple random survey, a margin of error of ±1% at 95% confidence requires about 9,600 respondents (under the most cautious assumption of a 50% proportion). A quick count can work with fewer stations because stations are stratified using data from previous elections, and each station carries a large amount of vote information. But the basic principle stays: the tighter the promised precision, the bigger and neater the sample must be, and the more the quality of data transmission matters. If an organization promises very tight precision with a very small sample, ask politely about its methodology.

    Read also: [Market research and survey services](https://datalyticsindo.com/en/market-research-survey/)


    Planning a survey, poll, or field study whose methodology must stand up to scrutiny? The datalytics.indo team helps from survey design and sampling, through analysis, to reporting that is honest about uncertainty. Private tutoring and in-house training on survey methodology are also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • The Rice Scale and the Gold Scale: Understanding Validity and Reliability Without the Headache

    If there is one topic that confuses students and early-career researchers the most, it is probably validity and reliability. Those two words appear in every research proposal, are demanded by every examiner, and are often answered with numbers copied from SPSS output without being truly understood.

    Let us use one simple analogy. Imagine you want to weigh yourself. The right instrument is a bathroom scale. If you use a rice scale, it may show a number, but the result cannot be trusted for that purpose. If you use a very sensitive gold scale, the result may be extremely precise, but the instrument was not designed for the weight of a human body.

    That is the essence of validity and reliability. Reliability asks: is this instrument consistent? Validity asks: does this instrument measure what it is supposed to measure? Both are needed, and they are not the same.

    Reliability: the consistency of a measuring instrument

    A reliable instrument produces consistent results when used repeatedly under the same conditions. A scale that shows 60 kg today, 72 kg two minutes later, and then 55 kg is clearly not reliable. In questionnaire research, there are several ways to assess reliability:

    • Test-retest. The same instrument is given to the same respondents at two different times. If the results differ greatly even though conditions are the same, the instrument is unstable. The condition is that what is being measured is assumed not to change much over that time.
    • Parallel forms. Two equivalent versions of the instrument are given, and the results are compared.
    • Internal consistency. This is the most commonly used. We check whether the items meant to measure the same concept actually agree with each other. The most popular tool is Cronbach’s alpha. In PLS-SEM, the recommended measure is composite reliability.

    A common benchmark: an alpha or composite reliability of around 0.70 and above is considered adequate for general research, and higher for riskier decisions. But a benchmark is only a benchmark. Alpha is affected by the number of items, so long instruments tend to get higher alpha simply because they are long.

    Validity: are we measuring the right thing?

    Validity is harder to prove than reliability, because it concerns meaning, not just numbers. There are several kinds of validity evidence:

    • Content validity. Do the items cover all aspects of the concept to be measured? It is usually judged by experts or through a literature review. A job satisfaction instrument that only asks about salary has poor content validity, because job satisfaction is not only about salary.
    • Construct validity. Do the items truly form the intended concept? This is where factor analysis (exploratory or confirmatory) comes in. Items that measure the same concept should cluster on the same factor. In PLS-SEM, we check outer loadings, average variance extracted (AVE), and discriminant validity, which is evidence that different concepts really are different.
    • Criterion validity. Does the instrument’s score relate to other relevant measures? For example, does a selection test score predict employee performance several months later?

    Why the two are not the same

    This is the most often misunderstood part. Reliable does not mean valid. Imagine a broken rice scale that always shows exactly the same number every time you step on it. It is very consistent, yet it does not measure your weight correctly. Consistent, but wrong.

    Conversely, valid is reliable (to a degree). If an instrument truly measures what is intended, its results cannot be random.

    That is why an alpha of 0.90 proves nothing about validity. Many students write “this instrument is valid and reliable because Cronbach’s alpha = 0.92”. That sentence mixes up two things. Alpha only speaks about internal consistency. In fact, a very high alpha sometimes signals items that are too similar (redundant).

    Item analysis: checking one by one

    Besides assessing the instrument as a whole, we examine each item. A commonly used measure is the corrected item-total correlation: how strongly an item’s score correlates with the sum of the other items. An item with a low correlation (for example below about 0.30) is suspect: it may measure something else, be ambiguously written, or be answered carelessly. We also check how alpha changes if the item is deleted. But do not delete items mechanically. Consider theory first: an item that is important in content should be improved, not simply dropped.

    Practical steps to prepare a good instrument

    1. Start from theory. Define your concept clearly, and derive its dimensions and indicators from the literature review.
    2. Write clear items. One idea per item, simple language, no double-barreled or leading wording.
    3. Ask experts to review for content validity.
    4. Pilot test. Give it to a small group of respondents similar to the final sample, and ask what is confusing.
    5. Analyze the pilot results. Check item-total correlations, reliability, and factor structure.
    6. Revise, then retest on the main sample. Validity and reliability are assessed again on the actual research data, because an instrument that works well in one sample is not necessarily good in another.
    7. Report honestly. State the measures used, their values, and their interpretation, including any weaknesses found.

    The mistakes that happen most often

    • Taking a questionnaire from another study and claiming it is “already valid”. An instrument that is valid in population A is not necessarily valid in population B, especially if it has been translated.
    • Deleting items until the numbers look good. The instrument ends up with three highly consistent items, but it no longer covers the concept.
    • Ignoring content validity and relying only on statistics. Numbers cannot replace reasoning about meaning.
    • Mixing scales. An instrument with several dimensions has its alpha computed as one scale. Compute it per dimension.

    Validity and reliability are not an administrative ritual before the analysis. They are the guarantee that every number you analyze afterwards actually means something. If your scale is wrong, however sophisticated the analysis on top of it, the result is still wrong.

    A mini example: an eight-item job satisfaction instrument

    Imagine you build a job satisfaction instrument with eight items, then test it on 60 employees. The SPSS output gives two important things. First, the overall Cronbach’s alpha, say 0.84, which indicates good internal consistency. Second, the item-total statistics table. Suppose item 6 has a corrected item-total correlation of only 0.12 and alpha rises to 0.87 if that item is deleted. That item is suspect. But before deleting it, reread its wording. Maybe it is a negatively worded statement whose score was not reversed (reverse-coded), maybe it asks about something different (for example distance to the office rather than satisfaction), or maybe the sentence is ambiguous. Improving an item is often more appropriate than discarding it.

    After reliability, run a factor analysis to see whether the eight items really form one dimension, or two different dimensions (for example satisfaction with the work itself and satisfaction with compensation). If the analysis shows two dimensions, compute reliability for each dimension, not as one scale. That is the honest way to work: the data tells you the structure, and you adjust the analysis to that structure.


    Need help building an instrument, testing it, or interpreting the results of validity and reliability testing? The datalytics.indo team can help with everything from research design and questionnaires, through analysis (factor analysis, CB-SEM and PLS-SEM, regression, path analysis, and more), to interpretation. Private tutoring in SPSS and SmartPLS is also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • A Roadmap for Choosing a Statistical Test: From Research Question to the Right Tool in 5 Questions

    The question I receive most often from students and early-career researchers is not “how do I run this test in SPSS?” but “which test should I use?” And the answer is almost always: “it depends.” Depends on what? On a few things that can actually be answered with five simple questions.

    If you answer these five questions honestly before opening any software, you will avoid picking an unsuitable test, and the defense room becomes a much friendlier place.

    Question 1: What is the goal of the analysis?

    There are four main goals, and each points to a different family of tests:

    • Comparing (is there a difference between groups or over time?)
    • Relating (are two variables associated?)
    • Predicting or explaining (which variables influence another variable?)
    • Grouping or summarizing (is there a hidden structure in the data?)

    Write your goal in one ordinary sentence before choosing a test. “I want to know whether average satisfaction differs between new and long-standing customers.” That sentence already shows the direction: a comparison of two groups.

    Question 2: What is the measurement scale of your variables?

    The measurement scale determines which mathematical operations make sense.

    • Nominal: categories without order (gender, city, brand).
    • Ordinal: ordered categories (education level, satisfaction ranking).
    • Interval/ratio: numbers with meaningful distances (income, age, test score, body weight).

    Likert variables are often treated specially. A single Likert item is strictly ordinal, while a combined score from many items is often treated as interval. That practice is common, but it should be stated and justified.

    Question 3: How many groups are compared, and are they independent or paired?

    Two questions in one. How many groups? Two, or more than two. Independent or paired? Independent means the groups consist of different subjects (for example men and women). Paired or repeated means the same subjects are measured more than once (for example scores before and after training) or matched pairs.

    Question 4: Are the assumptions of parametric tests met?

    Parametric tests (for example the t-test and ANOVA) assume certain things, such as a roughly normal distribution and comparable variances across groups. If those assumptions are clearly violated (for example a small sample with very skewed data, or ordinal data), a non-parametric alternative that does not rely on distributional assumptions is usually safer. But remember: non-parametric tests also have assumptions and are generally less powerful when the parametric assumptions are actually met.

    Question 5: What is the size and nature of your sample?

    A very small sample limits the choice of tests and makes assumption checks unreliable. A clustered sample (for example students within classes) violates the independence assumption and calls for special approaches (for example multilevel models).

    Quick selection tables

    Here is the short guide I use as a starting point. It does not replace judgment, but it saves time.

    Comparing groups on a numeric/ordinal variable

    SituationIf parametric assumptions are metNon-parametric alternative
    Two independent groupsIndependent samples t-testMann-Whitney test
    Two paired groupsPaired t-testWilcoxon test
    Three or more independent groupsOne-way ANOVAKruskal-Wallis test
    Three or more measurements on the same subjectsRepeated-measures ANOVAFriedman test

    Categorical variables

    SituationTest
    Relationship between two categorical variables (independent groups)Chi-square test (or Fisher’s test if expected frequencies are small)
    Dichotomous change in the same subjects (before-after)McNemar’s test
    Three or more dichotomous measurements on the same subjectsCochran’s Q test

    Relating variables

    SituationMeasure
    Two numeric variables, linear relationshipPearson correlation
    Ordinal data or assumptions not metSpearman or Kendall correlation
    Two categorical variablesPhi, Cramer’s V

    Predicting or explaining

    SituationTechnique
    One numeric dependent variable, one predictorSimple linear regression
    One numeric dependent variable, many predictorsMultiple linear regression
    Binary dependent variable (yes/no)Logistic regression
    Many relationships at once among latent variablesSEM or PLS-SEM
    Direct and indirect effects among observed variablesPath analysis

    Three good habits when choosing a test

    1. Decide on the test before seeing the results. Choosing a test after seeing which one gives a significant result is a recipe for false findings. Write your analysis plan at the start.

    2. Always report effect sizes and confidence intervals, not just p-values. Every test has a suitable effect size: Cohen’s d for a difference between two means, eta squared for ANOVA, regression coefficients for regression, and so on.

    3. Check assumptions on the right object. Normality in a t-test is checked within each group, and in regression on the residuals, not on the pooled raw variable.

    One complete example

    A training manager wants to know whether a new training program improves employees’ competence scores. She measures the same score on 40 employees before and after the training.

    • Goal: compare two measurements.
    • Scale: competence score (interval).
    • Groups: one group, two measurements, paired.
    • Assumptions: what is checked is the normality of the difference between the after and before scores.
    • Choice: paired t-test (if the differences are roughly normal) or Wilcoxon test (if not).
    • Reporting: the mean difference, its confidence interval, the effect size, and a practical explanation.

    The same five questions guide almost every test choice, from the simplest to the most complex. Mastering the logic is far more valuable than memorizing software menus.

    Three more examples to build intuition

    Example 1. A researcher wants to know whether education level (high school, bachelor’s, master’s) is related to the choice of digital payment method (three types of e-wallet). Both variables are categorical, with independent groups. The choice: Chi-square test, with Cramer’s V as a measure of association to show the strength of the relationship.

    Example 2. A team wants to compare task completion time across four interface designs, each tried by different people. Numeric variable, four independent groups. If the residuals are roughly normal and variances comparable: one-way ANOVA with a post hoc test. If the data is highly skewed and the sample small: Kruskal-Wallis.

    Example 3. A manager wants to predict whether a customer will cancel a subscription (yes or no) from subscription length, number of complaints, and usage frequency. Binary dependent variable, mixed predictors. The choice: logistic regression, evaluated with measures such as recall, precision, and AUC.

    A short assumptions checklist

    Before trusting the result of a t-test or ANOVA, check: independence of observations, normality (within groups or of residuals), and homogeneity of variance (for example Levene’s test). For regression: linearity, independence of errors, homoscedasticity, normality of residuals, and absence of severe multicollinearity. If an assumption is clearly violated, do not stop there: consider a transformation, a test that is more robust to violations, or a more suitable model.

    Short Q&A

    What if I am comparing two groups but the sample sizes are very unbalanced? A t-test with a correction for unequal variances (Welch’s test) is usually safer than the standard t-test. Also note that a very small group limits precision, whatever the test.

    Is it acceptable to run many tests on the same data? Yes, as long as you report all of them and account for multiple testing. The more tests you run, the greater the chance of finding a ‘significant’ result by chance, so the significance threshold needs to be adjusted or the results interpreted more carefully.


    Unsure which statistical test fits your research? The datalytics.indo team can help with everything from formulating the research question and designing the analysis, through carrying it out (regression, CB-SEM and PLS-SEM, path analysis, difference tests, non-parametric tests, factor analysis, clustering, and more), to interpretation. Private tutoring in SPSS and in-house applied statistics training are also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • 25 Variables Is Too Many? How to Summarize Them with Factor Analysis and PCA Without Losing Important Information

    Imagine a financial analyst asked to assess the health of companies in one industry. Based on prior research, there are 25 financial ratios worth watching: liquidity, solvency, profitability, efficiency, and so on. Analyzing 25 numbers for every company, then comparing them across companies, is exhausting work, and the result is often confusing because many of those ratios are related to each other.

    What if those 25 ratios could be summarized into three to five simpler indices, without losing the important information?

    That is what Principal Component Analysis (PCA) and Factor Analysis offer. They are among my favorite methods because they always feel like a magic trick that can be explained: what looks complicated turns out to have a simpler structure behind it.

    The core idea: many variables actually measure the same thing

    Variables in a dataset often overlap. For example: income, monthly spending, vehicle ownership, and house size. Technically they are different, but they very likely move together because they all reflect one big thing: “level of affluence”. If we can summarize the four into one affluence index, our analysis becomes more compact and often more stable.

    Some practical uses of these methods:

    1. Summarizing many variables into a few indices, like the financial ratios example above.
    2. Dealing with multicollinearity in regression. If several explanatory variables are so strongly correlated that they make regression estimation difficult, but all of them should still be used, we can form new variables (components) that are uncorrelated with each other, and use them in place of the original variables.
    3. Testing the structure of a questionnaire. For an instrument with many items, we want to know whether the items cluster according to the theoretical dimensions. This is part of construct validity testing.
    4. Visualization. Data with dozens of dimensions can be projected into two or three dimensions so that group patterns are easy to see.

    PCA and factor analysis: similar, but not the same

    They are often discussed together and often run from the same menu in software, but their purposes differ.

    PCA is a data reduction technique. It forms new components that are linear combinations of the original variables, arranged so that the first component captures the largest variance, the second captures the largest remaining variance uncorrelated with the first, and so on. Its focus: summarizing total variance.

    (Exploratory) factor analysis is a modeling technique. It assumes there are latent factors (unobserved concepts, such as “satisfaction” or “affluence”) that cause the variables we measure to be related. Its focus: explaining the correlations among variables through a few common factors, and separating common variance from each variable’s unique variance.

    Rule of thumb: if your goal is to summarize data or build an index, PCA is enough. If your goal is to understand the structure of the concepts underlying questionnaire items, factor analysis is conceptually more appropriate. In many theses the two are mixed up, and a sharp examiner will ask about the difference.

    Practical steps

    Here is the framework I use, in SPSS or other software:

    Step 1: Check whether the data is suitable. Two common tests: KMO (Kaiser-Meyer-Olkin), which measures sampling adequacy and ideally is above 0.50 (the higher the better), and Bartlett’s test, which tests whether the correlation matrix differs from an identity matrix (we want a significant result, because it means there are correlations among variables that can be summarized). If your variables are barely correlated with each other, there is nothing to summarize.

    Step 2: Decide the number of components or factors. There are several criteria, and they are best used together: (a) eigenvalues greater than 1 (Kaiser criterion), (b) the scree plot, looking for the “elbow” where the curve starts to flatten, (c) the cumulative percentage of variance explained (a target of around 60% or more is often used in the social sciences), and (d) ease of interpretation. Do not just follow the eigenvalue criterion mechanically, because it tends to produce too many components.

    Step 3: Rotate (if relevant). Initial results are often hard to interpret because many variables load on several components at once. Rotation (for example varimax) turns the axes so that each variable tends to load high on only one factor. This does not change the total variance explained, it only makes the pattern easier to read.

    Step 4: Read the loading matrix. Loadings show how strongly a variable relates to a factor. As a benchmark, a loading of about 0.50 or more is usually considered meaningful in medium-sized samples, and an item that loads high on two factors at once (cross-loading) needs to be reconsidered.

    Step 5: Name and interpret. Look at the variables that gather on one factor, then ask what they have in common. In the financial ratio example, one group might load liquidity ratios (“liquidity factor”), another group loads profitability ratios, and a third loads debt ratios.

    Step 6: Use the scores. Each respondent’s component or factor scores can be saved and used in further analysis, such as regression, clustering, or comparisons across groups.

    Common mistakes

    • A sample that is too small. These analyses need an adequate sample. A rough, often-quoted guideline is several times the number of variables, and no fewer than about 100 respondents. Small samples produce unstable solutions.
    • Including unsuitable variables. Nominal categorical variables are not suitable for this analysis in its standard form.
    • Ignoring theory. If the analysis produces factors you cannot explain substantively, you are looking at a statistical artifact, not a real concept.
    • Using exploratory factor analysis to prove a theoretical model. To test a structure already specified by theory, use confirmatory factor analysis.
    • Deleting as many items as possible until the result looks tidy. If you delete half the questionnaire for a good structure, your instrument no longer represents the concept.

    A simple workplace example

    An HR manager has an engagement survey with 30 statements. Instead of reporting 30 scores to the board, she runs a factor analysis and finds that the items cluster into five dimensions: leadership, compensation, workload, career development, and communication. The report becomes five easy-to-read indices, and comparisons across divisions become more meaningful. That is the practical value of this method: not just a technique, but a way to make information manageable.

    Having a lot of data is not the problem. Data that cannot be read is the problem. And with the right tools, a lot of data can be summarized into a clear story.

    An example of reading a loading table

    Imagine the varimax-rotated result for six financial variables produces two factors. The variables current ratio, cash ratio, and working capital have loadings of 0.86, 0.81, and 0.77 on Factor 1, but below 0.20 on Factor 2. The variables profit margin, ROA, and ROE have loadings above 0.80 on Factor 2 and below 0.15 on Factor 1. The pattern is clean: Factor 1 can be named ‘liquidity’ and Factor 2 ‘profitability’. If one variable, for example the debt ratio, loads 0.45 on both factors, it is ambiguous, and you need to decide whether to drop it, keep it, or review it theoretically. That decision must be explainable in the methods chapter.


    Need help with factor analysis, PCA, construct validity, or summarizing a questionnaire with many items? The datalytics.indo team can help with everything from research design and questionnaires, through analysis (factor analysis, clustering, regression, CB-SEM and PLS-SEM, path analysis, and more), to interpretation. Private tutoring in SPSS and SmartPLS is also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • Ice Cream and Drowning: Why Correlation Is Not Causation (and How to Test It Properly)

    In statistics lectures, there is one classic example that never gets boring. Researchers collect monthly data and find that when ice cream sales rise, the number of drowning cases rises too. The correlation is strong. The chart is pretty, two lines moving up and down together like two dancers who have rehearsed.

    The question: should we ban ice cream at the beach?

    Of course not. And you have probably guessed why. Hot weather makes people buy more ice cream, and hot weather also makes more people swim. More people swimming means more people drowning. Ice cream and drowning both rise because of a third cause. Statisticians call it a confounder.

    The example is funny, but the same mistake happens every day in the real world: in company reports, in the news, and, most often, in theses. Let us take it apart so you do not get fooled.

    What exactly is correlation?

    Correlation measures how strongly two variables move together. Its value (the correlation coefficient) ranges between −1 and +1. Close to +1 means both tend to rise together, close to −1 means one rises when the other falls, and around 0 means there is no clear linear pattern.

    The method depends on the measurement scale of the variables. For two numeric variables with a linear relationship, we use Pearson correlation. For ranked data or data that does not meet the assumptions, we use Spearman or Kendall. For two categorical variables (for example gender and product choice), we use measures of association such as Phi or Cramer’s V. These tools are useful, but they all answer the same question: “do the two move together?” Not: “does one cause the other?”

    Four reasons two things can correlate without causing each other

    1. A confounder (a third cause). Like ice cream and drowning. Another example: people who carry matches in their pockets are more likely to get lung cancer. It is not the matches that cause it, but the smoking habit that makes them carry matches.

    2. Reversed direction of cause and effect. We suppose A causes B, when B actually causes A. For example, you find that employees who attend training more often perform better. Maybe training improves performance, but maybe managers more often send already high-performing employees to training.

    3. Coincidence. If you search enough pairs of variables, some pairs will appear correlated by chance alone. There are websites that collect silly correlations, such as per capita cheese consumption tracking the number of people who died by becoming tangled in their bedsheets. The correlation is high, the meaning is zero. The more hypotheses you test, the greater the chance of finding a false relationship.

    4. A deceptive pattern because data is combined (Simpson’s paradox). A trend visible in the combined data can reverse when the data is split into groups. For example, a hospital looks worse than another overall, but when viewed by patient severity, it is actually better at every level. The reason: that hospital receives more patients in serious condition. Combining data without thinking about its composition hides the truth.

    So how can we claim cause and effect?

    Establishing cause and effect is harder than computing a correlation, and it demands design, not just formulas. There are several approaches, from the strongest:

    • Randomized controlled experiments. Researchers randomly assign subjects to treatment and control groups. Because assignment is random, known and unknown confounders tend to be balanced between groups. This is the gold standard, but it is not always possible or ethical.
    • Natural experiments and quasi-experimental designs. When we cannot randomize, we look for natural situations that resemble randomization, or compare changes before and after a policy between affected and unaffected groups (for example a difference-in-differences design).
    • Statistical control. We include known confounders in a regression model to “remove” their influence. This is useful, but only as good as the list of confounders you know and measure. Unobserved confounders remain dangerous.
    • Theoretical reasoning and layered evidence. In fields that are hard to experiment in (for example epidemiology), cause-and-effect conclusions are built from many studies, plausible mechanisms, a clear time order, and consistency of findings.

    For a thesis with a one-time survey, the practical message is this: use language proportionate to your design. Write “is related to” or “is associated with”, not “causes” or “has an impact on”, unless your design truly supports it. And state plainly that you cannot rule out other explanations.

    An example from the workplace

    Suppose the HR department finds that employees who joined a mentoring program have a lower turnover rate. The tempting conclusion: “Mentoring lowers turnover, let’s extend it to all employees.” But before deciding, ask:

    • Who joined mentoring? If more motivated employees are more likely to sign up, the difference may reflect motivation, not the effect of mentoring.
    • Are there other differences between participants and non-participants (division, tenure, salary)?
    • Can we test it through a limited pilot with random selection?

    Those questions may seem to slow things down, but they actually save money. Expanding a program whose effect is illusory costs far more than running a careful small pilot.

    A quick way to detect misleading claims

    Whenever you hear a claim that “A causes B”, ask these five questions:

    1. Could B be causing A?
    2. Is there a third thing causing both?
    3. Could the relationship arise purely by chance (how many other relationships were tried)?
    4. Is there a fair comparison, meaning a group that is similar except for A?
    5. Is there a plausible mechanism explaining how A affects B?

    If the claim fails three of the five questions, treat it as a hypothesis, not a fact.

    Ice cream does not make people drown. But the habit of drawing conclusions from two lines that move together has “drowned” a lot of business decisions and research.

    How to report a correlation properly

    A well-reported correlation includes five things: the coefficient (for example r = 0.42), the number of observations, the confidence interval, the p-value as a supplement, and a scatterplot. The scatterplot matters because the same number can come from very different patterns. There is a classic example called Anscombe’s quartet: four datasets with nearly identical means, variances, and correlations, but with completely different shapes, some a straight line, some curved, some driven by a single outlier. Without looking at the chart, we can conclude the wrong thing.

    To interpret the strength of a relationship, a commonly used guideline (which is rough and depends on the field) calls an absolute value of about 0.10 weak, 0.30 moderate, and 0.50 and above strong. But in the social sciences, a correlation of 0.30 is often already considered meaningful. So the context of the field needs to be considered.


    Need help testing relationships between variables in your data with the right method and interpreting them honestly? The datalytics.indo team can help with everything from research design, through analysis (correlation, regression, CB-SEM and PLS-SEM, path analysis, factor analysis, clustering, and more), to interpretation. Private tutoring and in-house training are also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.

  • SEM or PLS-SEM? How to Choose Without Relying on “People Say It’s Easier”

    Every thesis season, one question flows to me almost nonstop: “Should I use LISREL or SmartPLS?” And almost always, behind that question is the same reason: “My friend says SmartPLS is easier.”

    I understand. As someone who has written teaching modules on both approaches, I will not deny that SmartPLS is friendly on screen. But choosing an analysis method because of “whichever looks friendlier” is like choosing a vehicle by its color. It may be pleasant, but it does not mean you will reach your destination.

    This article tries to offer a healthier way of thinking about choosing between two families of Structural Equation Modeling (SEM): covariance-based SEM (CB-SEM) and variance-based SEM (PLS-SEM).

    First, what is SEM?

    SEM is a single analytical framework that can answer several questions at once. It describes the relationships between latent variables (concepts that cannot be measured directly, such as satisfaction, motivation, or trust) and their indicators, as well as the relationships among the latent variables themselves. The main advantage of SEM over ordinary regression is that it accounts for measurement error and analyzes many relationships in one model.

    One thing I always remind people: SEM is not just a technique, it is a way of thinking. You start from theory, draw the model, and only then test whether the data supports the theory. If you reverse that order (run the software first, look for theory afterwards), the results are usually a mess.

    Two families, two philosophies

    CB-SEM (for example LISREL, AMOS, Mplus, or the lavaan package in R) tries to reproduce the covariance matrix of the data. The main question: does my theoretical model fit the pattern of relationships in the data? That is why it produces many goodness-of-fit measures such as RMSEA, CFI, TLI, and SRMR. CB-SEM suits testing and confirming theory.

    PLS-SEM (for example SmartPLS) works with a variance-based approach. It tries to maximize the explained variance of the dependent variable. The main question: how well does this model predict and explain the variables I have linked? PLS-SEM suits theory development and prediction.

    One philosophical difference, two ways of judging quality. That is the root of every technical difference below.

    When does CB-SEM make more sense?

    • Your main goal is to test a well-established theory, and you want to know whether the whole model fits the data.
    • Your constructs are mostly reflective (indicators are seen as reflections of the construct).
    • Your sample is large enough and the data is close to the required distributional assumptions (or you use an estimator that is more robust to violations).
    • You need advanced features such as testing measurement invariance across groups.

    When does PLS-SEM make more sense?

    • Your main goal is prediction or exploration of a model whose theory is not yet mature.
    • Your model is complex, with many constructs and indicators.
    • You have formative constructs (indicators “form” the construct rather than being reflected by it).
    • Your data does not meet normality assumptions, or the sample is relatively small, although this point is often misunderstood (see below).

    Three myths to clear up

    Myth 1: “PLS-SEM suits small samples, so any sample size is safe.” PLS-SEM is indeed more tolerant than CB-SEM of small samples and non-normal data, but that does not make it magic. Small samples still produce unstable estimates. The often-quoted “ten times” rule is criticized for being too crude. Sample requirements still depend on model complexity and the effect size you want to detect.

    Myth 2: “PLS-SEM has no fit measures, so it is easier to pass.” The measures are different, not absent. In PLS-SEM we assess the measurement model through outer loadings (usually ≥ 0.70 as a benchmark), composite reliability, average variance extracted (AVE ≥ 0.50), and discriminant validity (for example HTMT). The structural model is assessed through R², effect sizes, predictive relevance (Q²), and the significance of path coefficients via bootstrapping. The evaluation is no looser. It just speaks a different “language”.

    Myth 3: “One approach is certainly superior.” There is no such thing. Both are tools, and both can be used wrongly. Many studies reach substantively similar results when the model and data meet the requirements of both approaches.

    Guiding questions before you choose

    When someone brings me a research proposal, I usually ask the following five questions:

    1. Is your main goal to test theory or to predict? Testing theory leans toward CB-SEM; prediction leans toward PLS-SEM.
    2. What is the nature of your constructs: reflective or formative? Formative leans toward PLS-SEM.
    3. How large is your sample, and how is the data distributed? A very small sample and very non-normal data give a stronger reason for PLS-SEM, but with care.
    4. How mature is your theory? A theory that is still taking shape suits an exploratory approach better.
    5. What do your examiner or target journal expect? This is not a scientific reason, but it is a realistic one. If the journal you are aiming for usually uses one approach, understand why and prepare your argument.

    The mistake I see most often

    It is not choosing LISREL over SmartPLS or the reverse. The most common mistake is being unable to explain why you chose. At a thesis defense, the question “why did you use PLS-SEM?” gets answered with “because my sample is small” or “because it is easier”. A good examiner expects an answer grounded in the research objective, the nature of the constructs, and the characteristics of the data.

    The second mistake: skipping the evaluation of the measurement model and jumping straight to reading path coefficients. That is like reading a scale’s result without checking that the scale is accurate. Validity and reliability must be settled first; only then do the relationships between variables mean anything.

    The third mistake: making significance the only goal. A model where “everything is significant” is not necessarily meaningful. Look at effect sizes, explanatory power, and whether the relationships make sense theoretically.

    Conclusion: choose with reasons, not comfort

    SEM versus PLS-SEM is not about who wins. The question is: what do you want to learn from your data, and which tool answers it most honestly? Answer with reasons you can defend, and you will be calmer both in front of your examiner and in front of a journal reviewer.

    Two realistic scenarios to build intuition

    Scenario A. A lecturer wants to test a well-established theory: service quality affects satisfaction, and satisfaction affects loyalty. She has 500 respondents, all constructs are reflective scales from validated instruments, and she wants to know whether the model “fits” the data and whether it is equivalent for men and women. This is territory for CB-SEM.

    Scenario B. A manager wants to understand which factors best predict the success of a customer retention program. The model includes several new constructs with no standard instrument, one of them an index formed from several different indicators (formative), and he has only 120 respondents. The goal is prediction and exploration. This is better suited to PLS-SEM, with the caveat that 120 samples need to be checked for adequacy against the model’s complexity.

    Notice that the choice is not decided by the software available, but by the objective, the nature of the constructs, and the data. Whatever you choose, write your reasons in the methods chapter in a few clear sentences. That alone separates research that was thought through from research that was merely run.


    Unsure which SEM approach to pick, setting up your model, or interpreting the output? The datalytics.indo team can help with everything from research design and instrument testing, through analysis (CB-SEM and PLS-SEM, path analysis, regression, factor analysis, clustering, and more), to interpretation and writing up the results. Private tutoring in SmartPLS, LISREL/AMOS, and SPSS is also available. Let’s discuss your needs first. We’ll provide a tailored quote based on your project.