Risk Information and Skin-cancer Education for Undergraduate Prevention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Risk Information and Skin-cancer Education for Undergraduate Prevention (NCT03979872), a randomized na study. The primary outcome is Sun Protection Behaviors Assessed Via Questionnaires.

2. Clinical Question

The study asks whether adding personalized information to skin-cancer education is associated with differences in reported sun-protection behaviors among undergraduate students. The personalized components were a UV photograph intended to show existing skin damage and MC1R genetic testing based on a saliva sample. The education-only group provides the reference condition for considering the additional components.

The study also lists questionnaire outcomes concerning sunburn, intentional outdoor tanning, intentional indoor tanning, and tan occurrence. These are separate behavioral outcomes, not substitutes for the primary sun-protection score. The registry record does not report results for these secondary outcomes either, so the available record cannot establish whether the groups differed on them.

3. Trial Design

The registry record describes a randomized, single-masked, parallel study with four groups. Each group received skin-cancer education. One group received education only; another received education and a UV photograph; another received education and MC1R testing; and the final group received education, a UV photograph, and MC1R testing. Randomization means assignment was intended to occur by chance. The identity of the person or people masked is not reported in the registry record.

The record lists enrollment as 92 and the study status as completed. Its recorded start date is 2019-09-09, and primary completion is recorded as 2020-04-07. The brief description says the study would last between 2-3 months. The primary outcome timeframe lists Visit 1 at Week 0, Visit 2 at Week 4, and Visit 3 at Week 8. The planned follow-up methods included phone, text messages, or e-mail between study visits.

The principal outcome was sun-protection behavior assessed by questionnaire. Participants were asked how often they had engaged in specified behaviors when outdoors in the sun for 15 minutes or more during the past four weeks. The record describes a score from 1 to 5, with higher scores indicating greater likelihood of sun-protection habits. It identifies the outcome as a mean with standard deviation for each behavior at each visit.

The record notes that the number analyzed at each visit differed from the overall number analyzed in each arm because of participant attrition over time. The visit-specific numbers and the methods used to handle missing observations are not reported in the registry record. Although the study was randomized, details such as the randomization procedure and allocation concealment are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Analysis population for the primary outcome, as defined in the registry: The difference in the number of participants analyzed at each visit versus overall participants analyzed for each study arm is due to participant attrition over time.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Sun Protection Behaviors Assessed Via Questionnaires, measured over Weeks 0 (Visit 1), 4 (Visit 2), 8 (Visit 3).

The primary endpoint is sun-protection behavior assessed through questionnaires. Participants were asked about what they had done in the past four weeks when outdoors in the sun for 15 minutes or more. The recorded response scale ranges from 1 to 5; higher scores indicate participants were more likely to engage in sun-protection habits. The registry record calls for a mean and standard deviation for each behavior at baseline and the two follow-up visits.

Questionnaire-based behavior measures are used to capture reported habits that may be relevant to prevention education. They are not direct measurements of skin damage or future cancer, and the record does not describe them as such. Their interpretation depends on the wording of the questions, participants’ recall, and the scoring approach. The record gives an example of the question framing and score direction, but does not provide the individual behavior items or their separate results.

The scheduled measurements are at Week 0 (Visit 1), Week 4 (Visit 2), and Week 8 (Visit 3). Comparing these time points could describe how reported behaviors changed during the study, while comparing arms could describe differences between the assigned educational approaches. However, the registry record does not report arm-specific means, standard deviations, changes over time, or inferential comparisons. It therefore defines the endpoint but does not establish what the endpoint results were.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the outcome summary represent?

The primary measure is described as a mean with standard deviation for each sun-protection behavior. A mean gives a summary of the scores in a group, while a standard deviation describes how spread out individual scores are around that mean. These are descriptive statistics: they characterize the observed responses but do not, by themselves, estimate how reliably one arm differs from another. The registry record does not report the actual means or standard deviations.

General: a difference between group means is an effect estimate. It expresses the contrast in the score scale’s units, which in this study is a scale from 1 to 5. To assess precision, an estimate is commonly paired with a confidence interval. A confidence interval describes uncertainty around an estimate under the statistical model and sampling assumptions; it is not a guarantee that the true effect lies within its limits. The registry record does not report a primary-outcome effect estimate or confidence interval.

How should the repeated visits be understood?

The outcome timeframe includes baseline at Week 0 and follow-up at Week 4 and Week 8. Because the same study follows participants across visits, measurements are repeated rather than independent snapshots of unrelated groups. General: statistical methods for repeated measurements account for the fact that observations from the same participant may be related. A model could estimate change over time, differences between arms, or whether changes differ by arm, depending on the prespecified question and method. The statistical model and the particular comparisons used are not reported in the registry record.

Looking separately at each visit is not the same as estimating a change from baseline or a difference in change between arms. Such analyses answer different questions and can yield different estimates. The record defines measurements at each visit but does not state whether the reported analysis was intended to compare scores at individual visits, changes from baseline, or trajectories across visits. It does not report numerical results for any of these possibilities.

What does randomization contribute?

General: random assignment is intended to make treatment groups comparable, on average, with respect to measured and unmeasured characteristics at the point of assignment. It does not guarantee that groups are identical, particularly in a study with several arms. The registry record identifies the study as randomized but does not describe sequence generation, concealment, or the handling of departures from assigned group. It also does not identify who was masked. Those details limit assessment of how the design was implemented.

Randomization supports comparisons according to assigned groups when analyzed appropriately. It does not remove the need to report group-specific results, participant flow, missingness, and the analysis method. In particular, attrition after assignment can affect which observations contribute at later visits. General: if missingness is related to participants’ outcomes or characteristics, analyses restricted to observed responses may not represent all randomized participants. The registry record acknowledges attrition but does not report enough information to evaluate its potential impact.

How do multiple arms and outcomes affect interpretation?

The four arms combine education with different additions: a UV photograph, MC1R testing, or both. Several possible contrasts could be chosen. For example, a comparison of the combined intervention with education alone differs from comparisons that isolate one added component. General: when several comparisons or outcomes are tested, the chance of at least one apparently unusual result can increase if multiplicity is not considered. Methods may address this by defining a primary contrast in advance, adjusting inference, or clearly labeling secondary and exploratory analyses. The registry record does not report a multiplicity strategy or identify a primary contrast among the arms.

The primary endpoint includes multiple sun-protection behaviors and multiple visits, and the secondary outcomes include several additional behaviors. The registry record does not provide a single reduced comparison for the primary outcome. This means that one should not treat the study as if it had a single, fully specified arm-to-arm test unless the analysis record establishes that. The chosen outcome, visit, contrast, and method all affect the meaning of a statistical result.

What do planning calculations mean?

General: a sample-size calculation estimates the number of participants needed to target a stated ability to detect an effect under specified assumptions. It is a planning exercise, not a measure of the chance that a completed study has found a true effect. The registry record describes an illustration based on a fraction of the observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It does not report the numerical planning outputs or the underlying observed effect in the information available for interpretation.

Any such illustration should be understood as conditional on its assumptions. It does not replace the trial’s actual results, and it is not observed power. The study has four arms, while the stated planning assumptions refer to equal allocation between two arms; the record does not report which comparison the illustration represents. It also does not report the trial’s own sample-size justification or statistical plan. Those omissions make it inappropriate to use a planning illustration to infer the design rationale or the precision of the completed study’s findings.

Overall, statistical interpretation requires the outcome estimates, their uncertainty, analysis populations, handling of missing observations, and the comparisons that were specified. Those analysis details are not reported in the registry record. General statistical principles can explain how such details matter, but they cannot recover the missing study results.

10. Multiplicity, Missing Data and Analysis Populations

The study includes four randomized arms, three measurement visits for the primary outcome, several sun-protection behaviors, and secondary questionnaire outcomes concerning sunburn and tanning. This creates multiple possible results to report and interpret. General: multiplicity matters because repeated testing can make chance findings more likely to appear noteworthy. A prespecified primary contrast or an appropriate adjustment can help define how evidence should be judged across multiple tests. The multiplicity strategy, the hierarchy of outcomes, and the prespecified contrasts are not reported in the registry record.

The record says that the number analyzed differed by visit because of participant attrition over time. It does not report visit-specific analysis counts, reasons for missingness, or how missing responses were handled. Methods such as analyzing available observations, imputing missing values, or using a repeated-measures model rely on different assumptions. Which method was used is not reported in the registry record, so the impact of missing data cannot be evaluated.

The analysis population is also not reported in the registry record. It is therefore unclear whether analyses were based on all participants as randomized, participants who completed particular visits, or another defined population. No statistical analysis results are posted in the registry record, and the statistical plan, interim analyses, and sample-size justification are not reported there. These gaps prevent a full assessment of how the analysis addressed multiple comparisons, attrition, and departures from the planned study procedures.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry record reports serious adverse events and other adverse events separately for each of the four arms. It lists 0 serious adverse events and 0 other adverse events in every arm. It also lists 0 deaths in every arm. The at-risk counts shown for these safety summaries are 22 for education alone, 23 for education plus a UV photo, 24 for education plus MC1R testing, and 23 for education plus both additions.

These figures describe the events recorded in the registry safety summary for the listed groups. A count of zero means that no event in that category was recorded in that group’s reported safety data; it does not prove that an event is impossible or that no unrecorded event occurred. The record does not provide event-level descriptions, follow-up duration for safety assessment, or details of how events were collected. The top serious-event terms are not listed.

Safety counts should also be read separately from the questionnaire outcomes. The absence of recorded adverse events does not supply evidence about sun-protection behavior, and the behavior endpoint does not determine the safety count. These registry figures are a limited summary, not a complete assessment of every potential risk.

12. What the Result Does, and Does Not, Mean

The record establishes that a randomized, parallel study compared skin-cancer education alone with education combined with a UV photograph, MC1R genetic testing, or both. It defines a primary questionnaire outcome focused on sun-protection habits, assessed at baseline and follow-up visits, and lists secondary questionnaire outcomes related to sunburn and tanning. It also reports the study as completed and gives an enrollment listing of 92.

What the record does not establish is whether any intervention combination changed reported behavior. Primary outcome scores, between-arm estimates, uncertainty intervals, and statistical tests are not reported in the registry record. Secondary outcome results are also not reported. Consequently, the effect’s direction, size, and precision cannot be described from this information. The endpoint definition and the fact of randomization are not substitutes for outcome data.

The study’s structure permits several possible comparisons, but the registry record does not specify which comparison was primary or describe the analysis method. It also notes attrition across visits without reporting its extent or the approach to missing observations. These omissions matter because the interpretation of repeated questionnaire measures depends on who contributed data at each visit and how the multiple arms, visits, and behaviors were handled.

The reported safety summary lists no serious adverse events, other adverse events, or deaths in the arms. Those counts describe the registry’s recorded safety data and do not establish that all risks are absent. They also do not answer the behavioral research question.

In short, the registry record supports a clear description of what was studied and what was intended to be measured. It does not support a conclusion that the approaches did or did not alter sun-protection behavior. Any stronger interpretation would require posted outcome results and sufficient details about analysis, missing data, and the comparisons performed.

13. Why This Trial Matters Statistically

This study is statistically interesting because it separates the common educational component from personalized additions. Its four-arm structure includes education alone, education plus a UV photograph, education plus MC1R testing, and education plus both additions. That design raises useful questions about how to distinguish the effect of each component from the effect of combining them. The registry record, however, does not report the contrasts or analysis plan used to answer those questions.

The outcome also illustrates the challenges of studying behavior through repeated questionnaires. The score is intended to reflect reported sun-protection habits, with higher values indicating greater likelihood of those habits. Repeated measurement at baseline and follow-up can describe patterns over time, but the analysis must account for within-participant dependence and attrition. The record acknowledges attrition but does not describe its statistical handling or report visit-specific scores.

Multiple arms, visits, behaviors, and secondary outcomes make clear reporting especially important. Readers need to know which outcome and comparison drove the main conclusion, how uncertainty was quantified, and whether multiple testing was addressed. Without those elements, the study’s design can be understood, but its statistical evidence cannot be weighed.

The record therefore serves as a reminder that a completed randomized study and a defined endpoint are only part of the evidence needed for interpretation. Clear reporting of estimates, precision, analysis populations, missing-data methods, and prespecified comparisons is essential for distinguishing a measurable difference from an uncertain or unsupported impression. Those analysis results are not reported in the registry record.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The principal limitation for interpretation is that the registry record defines the sun-protection endpoint without reporting its results. There are no arm-specific means or standard deviations, estimates of differences, uncertainty intervals, or p-values to evaluate. The secondary questionnaire outcomes are listed but their results are not reported either. As a result, the record cannot indicate the size, direction, or precision of any behavioral effect.

The outcome is self-reported. General: questionnaire responses can be affected by recall, interpretation of question wording, and the desire to give socially acceptable answers. The registry record does not report validation details for the questionnaire, its individual behavior items, or procedures intended to address such response effects. The score’s direction and range are described, but these details do not establish the measure’s reliability or sensitivity to change.

Attrition is explicitly noted, but its extent and consequences are not reported. Visit-specific participant counts, reasons for loss to follow-up, missing-data methods, and analysis populations are not reported in the registry record. Without those details, it is not possible to assess whether later observations could represent a selected subset of participants.

The record identifies randomization and single masking, but does not report the randomization procedure, allocation concealment, or who was masked. It also does not report the statistical plan, prespecified comparisons, handling of multiple outcomes, or sample-size justification. The study population is described as undergraduate students, and additional eligibility and setting details are not reported in the registry record. These limits constrain assessment of implementation, statistical validity, and how broadly any findings might apply.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Risk Information and Skin-cancer Education for Undergraduate Prevention — NCT03979872.
• Registry record last updated 2021-07-13; status last verified 2021-07.
• Results first posted 2021-07-01.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT03979872 is a completed randomized, single-masked, parallel study titled “Risk Information and Skin-cancer Education for Undergraduate Prevention.” The registry record lists enrollment as 92 and describes four groups: education alone, education plus a UV photograph, education plus MC1R testing, and education plus both additions. The recorded study start date is 2019-09-09, and primary completion is recorded as 2020-04-07.

The primary outcome is questionnaire-assessed sun-protection behavior, summarized as a mean and standard deviation at Week 0, Week 4, and Week 8. Higher scores on the scale from 1 to 5 indicate greater likelihood of sun-protection habits. The record also lists questionnaire outcomes for sunburn and tanning behaviors and notes attrition across visits.

Primary and secondary outcome results, statistical comparisons, uncertainty estimates, missing-data methods, and the statistical plan are not reported in the registry record. The safety summary lists 0 serious adverse events, 0 other adverse events, and 0 deaths in each arm.