The Skin Savvy Study: A Behavioral Skin Cancer Prevention Intervention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Skin Savvy Study: A Behavioral Skin Cancer Prevention Intervention (NCT00709306), a randomized na study. The primary outcome is Sun Stage of Change at 3 Months.

2. Clinical Question

The study was designed to investigate whether personalized UV-detect feedback and motivational interviewing could influence skin protection behavior, and to examine their effects individually and in combination. The record describes a pilot study, a formal randomized efficacy trial, and a dismantling study as parts of the broader proposed work. It does not make clear which of these components the enrollment and outcome record specifically represents, nor does it report the participant flow or the population included in the primary outcome analysis.

The primary outcome is a behavioral stage measure rather than a clinical diagnosis of skin cancer or a direct measure of cancer incidence. The question addressed by the recorded endpoint is therefore about participants’ reported current behavior and intentions at a specified follow-up, not about whether skin cancer was prevented.

3. Trial Design

The registry describes a completed randomized factorial study of skin cancer prevention interventions. It lists 197 participants and four groups: education control, motivational interviewing, UV-detect photographs, and UV-detect photographs with motivational interviewing. This arrangement represents the intervention components and their combination, but the record does not report the allocation ratio, sequence generation, concealment procedures, or the precise statistical contrasts planned for the factorial design.

The education control involved a packet of standard educational brochures and handouts from major professional organizations, which participants reviewed independently for 10-15 minutes. Participants assigned to motivational interviewing met with a trained counselor who reviewed personalized risk feedback from baseline assessments. The UV-detect photo group viewed regular and UV-filtered black and white photographs of the face. The combined-intervention group received motivational interviewing and UV-detect photographs. Further details of the intervention procedures are incomplete in the registry record.

Masking is listed as none. The record does not explain whether outcome assessment was conducted by masked staff, whether participants knew the study hypotheses, or whether counselors knew the assigned group. These details matter when interpreting a self-reported behavioral outcome, since participants and intervention providers can be aware of the intervention.

The listed study start is 2006-03, primary completion is 2008-06, and status is completed. The primary outcome is specified at 3 months. The record does not describe follow-up beyond that endpoint in the results, the length of follow-up for any other outcome, or how many participants contributed data at each assessment. It also does not report a sample-size justification or the planned model and contrasts for analyzing factorial effects.

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.

Before assignment: Participants were consented, baselined, and randomized upon arrival to the in-person session, thus no enrolled participants were excluded from the study before assignment to one of the four treatment conditions.

Overall Study

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 Stage of Change at 3 Months, measured over 3 months.

The primary endpoint is Sun Stage of Change at 3 months, recorded as a count of participants. The scale is described as having four items that ask about skin protection over the past year, current skin protection, intention to protect skin in the next 30 days, and intention to protect skin in the next year. The described response stages are maintenance, action, preparation, contemplation, and pre-contemplation, including a response for none of the other stages.

Stage measures are used to characterize where people report being in a behavior-change process. They distinguish reported current behavior from intention to change, so a single overall count would conceal meaningful differences between stages. The measure may therefore describe the distribution of participants’ reported behavior and intentions at follow-up. It is not itself a measure of skin cancer incidence, objectively measured sun exposure, or lasting behavior change.

The registry does not report the number of participants in each stage, a complete definition of how the four items were combined or scored, or the handling of responses that might not fit a single stage. It also does not report baseline stage counts alongside the 3-month assessment. Without those details and the outcome counts, the direction or size of any change cannot be assessed from the registry record. The endpoint description identifies what was intended to be measured, but does not establish the observed distribution or the comparison between groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods for the primary outcome cannot be fully reconstructed from the registry record. The record identifies a randomized factorial study and a count outcome at 3 months, but reports no analysis results and no detailed statistical plan. The explanations below describe general considerations for this kind of outcome; they are not claims about methods actually used in this trial.

What does a factorial design allow researchers to ask?

In general, a factorial design can evaluate more than one intervention component within one study. It can ask whether each component is associated with an outcome and whether the combination behaves differently from what would be expected from the components considered separately. To interpret such results, the analysis needs to define the target contrasts and how a possible interaction is handled. The registry labels this trial factorial and lists education, motivational interviewing, UV-detect photographs, and their combination, but the planned contrasts, model terms, and interaction analysis are not reported in the registry record. It would therefore be inappropriate to assign a particular factorial analysis to the study.

How should a stage outcome be analyzed?

As a general statistical matter, a set of ordered behavior stages can be represented in several ways. An analysis might preserve the separate categories, use an ordinal model, or compare a prespecified grouping of categories. Each choice answers a different question and can make different assumptions about the relationship among stages. A count of participants is descriptive until the categories, denominator, and comparison are specified. Here, the registry describes stage categories and gives the outcome unit as participants, but it does not report the outcome counts, a scoring rule, or the inferential model. No specific method can be attributed to the investigators.

What do confidence intervals and p-values contribute?

In general, a confidence interval expresses the range of effect estimates compatible with the data and the statistical model at a stated confidence level. Its width conveys precision: a wide interval indicates substantial uncertainty, while a narrower interval indicates more precise estimation under that model. A p-value evaluates how compatible the observed data are with a specified null hypothesis, conditional on the model and its assumptions. Neither quantity alone establishes clinical importance or proves that an intervention caused a difference. The registry record does not report confidence intervals, p-values, effect estimates, or the hypotheses used for testing.

Why can counts require special attention?

General methods for counts depend on what is being counted and how observations were collected. Counts of participants in mutually exclusive categories are different from repeated event counts for each participant. If the categories sum to a fixed group size, analyses should account for that structure; treating each category as an independent outcome can misrepresent uncertainty. The registry identifies a count of participants but does not give category-specific counts or clarify the analysis structure. The outcome should not be treated as a rate or repeated-event measure without evidence that it was collected that way.

What does over-dispersion mean in general?

For count models, over-dispersion means that the observed variability exceeds what a selected model assumes. If it is ignored, standard errors can be too small and confidence intervals can be too narrow. Methods that allow extra variation may be suitable in some count-data settings, but the choice depends on the outcome structure and model. There is no evidence in the registry record about whether over-dispersion was assessed or whether a count model was fitted. Moreover, the primary outcome’s description as a count of participants across behavior stages does not establish that a conventional event-count model is appropriate.

How does randomization relate to inference?

In general, random assignment supports comparisons between groups by balancing measured and unmeasured baseline characteristics on average, but it does not guarantee identical groups in a particular trial. The analysis still needs to account for the design and define which participants are included. Details such as allocation concealment, adherence, follow-up, and missing outcomes affect interpretation. The registry reports randomized allocation but does not report the randomization procedures, baseline balance, adherence, or analysis population. These omissions prevent a fuller appraisal of the analysis.

The record also does not report a sample-size justification, interim analyses, prespecified multiplicity control, or the statistical plan. No observed effect or effect estimate is available in the registry record for interpreting planning illustrations. A sample-size illustration based on an observed effect, when available, is a planning exercise rather than observed power and does not replace the trial’s original design justification.

10. Multiplicity, Missing Data and Analysis Populations

The trial lists multiple intervention groups and a primary outcome with several behavior stages. This creates potential multiplicity questions: investigators could compare multiple arms, test separate intervention components, examine a combination effect, or analyze several outcome categories. The registry record does not report which comparisons were prespecified, how many hypotheses were tested, or whether any adjustment for multiple testing was planned or used. Without that information, the risk of interpreting a chance finding as definitive cannot be evaluated.

Missing-data methods and participant flow are also not reported in the registry record. Although enrollment is listed as 197, the number with observed Sun Stage of Change data at 3 months is not reported. The record does not state how missing responses were handled, whether participants were analyzed according to assigned group, or whether sensitivity analyses were performed. These details are important because complete-case results can be biased if the likelihood of missing follow-up data is related to behavior or intervention assignment.

The analysis populations are not described. The record does not identify an intention-to-treat population, a per-protocol group, or another set of participants used for the primary analysis. It also does not report protocol deviations or intervention adherence. Therefore, the denominator and interpretation of any group comparison cannot be determined from the posted record.

The registry’s adverse-event entries are zeros in all listed groups, but the record does not explain whether this reflects no events, no reports, or a particular collection process. Missingness and reporting conventions for safety information are not described. These limitations do not establish that data were missing or that events occurred; they identify information needed to interpret the record fully.

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

The record establishes that a randomized factorial study examined education, motivational interviewing, UV-detect photographs, and their combination in a skin cancer prevention context. It identifies Sun Stage of Change at 3 months as the primary outcome and describes the behavior stages the measure is intended to capture. Those details clarify the study question and the kind of outcome the investigators selected.

The registry does not report the primary outcome counts or a statistical comparison. It therefore does not show whether participants in any group were more likely to report a particular stage, whether an intervention component was associated with a difference, or how uncertain an estimated effect might be. No conclusion about the size, direction, or statistical significance of an effect can be drawn from the posted results.

Even if stage counts were available, a behavioral stage measure would not by itself demonstrate a reduction in skin cancer. The scale concerns reported protection behavior and intentions; the registry does not report skin cancer incidence as the primary endpoint. Nor does a measurement at 3 months, without further follow-up results, establish that any behavior change lasted longer.

Randomization is a useful design feature for comparing assigned groups, but interpretation still depends on outcome availability, adherence, analysis methods, and prespecified comparisons. These are not described sufficiently to assess the primary analysis. Similarly, the zero adverse-event entries should not be expanded into a claim that no adverse events occurred, because the reporting context is not given.

The most defensible reading is that the record documents the intervention framework and intended behavioral endpoint, while leaving the central comparative result unavailable. The absence of reported results is not evidence of no effect; it is an absence of an interpretable estimate in the registry record.

12. Why This Trial Matters Statistically

Statistically, this study is notable for combining behavior-change interventions in a factorial framework and selecting a staged behavioral outcome. The design raises useful analytic questions about component effects and their combination, while the outcome makes clear that participant responses may occupy several distinct categories rather than one simple yes-or-no state. Interpreting such a design requires transparent definitions of the contrasts and category-level results.

The registry record also illustrates the difference between a study description and an analyzable result. It reports enrollment, groups, a primary endpoint, and the endpoint timeframe, but not the primary outcome counts, effect estimates, uncertainty intervals, or analysis methods. Without these, a reader cannot assess precision or compare groups, even when the trial design and outcome are clearly named.

Reporting the flow of participants, denominators for each group, stage distributions, and planned analysis would make the behavioral findings easier to interpret. Clear documentation of factorial contrasts and multiplicity decisions would further show how the study addressed its multiple intervention components. These are general reporting considerations, not claims about what the study team did.

The trial’s statistical importance is therefore partly methodological: it brings together intervention components and a multilevel behavior measure, but the registry record does not provide the results needed to evaluate those choices empirically. The design can motivate questions about personalized feedback and counseling, while the posted information remains insufficient to answer the comparative question.

13. 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.

A central limitation is that the registry record does not report results for the primary outcome. It gives no stage counts, comparative estimates, confidence intervals, or p-values. The intended endpoint is described, but its observed distribution at 3 months cannot be assessed.

Information about the study population is limited. Enrollment is listed as 197, but participant characteristics, recruitment procedures, eligibility criteria, and the number completing follow-up are not reported in the registry record. Generalizability and the representativeness of the analyzed participants therefore cannot be judged.

The endpoint description leaves important measurement details unresolved. The registry describes four items and multiple stages, but does not report the complete scoring rule, how responses were combined, or whether the outcome was analyzed by category or as a derived score. There is also no reported baseline distribution alongside the 3-month endpoint.

Details of implementation are incomplete. The motivational interviewing description is truncated, as is the description of the UV-detect photo intervention. The record does not give information on intervention fidelity, participant adherence, or whether the assigned interventions were delivered consistently. Masking is listed as none, and the record does not clarify whether outcome assessment was masked.

Finally, the analysis plan, handling of missing data, analysis populations, multiplicity procedures, and sample-size justification are not reported in the registry record. The adverse-event entries are all recorded as zero, but their reporting context is not explained. Together, these gaps limit assessment of bias, precision, safety reporting, and the meaning of any potential group differences.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: The Skin Savvy Study: A Behavioral Skin Cancer Prevention Intervention — NCT00709306.
• Registry record last updated 2018-08-31; status last verified 2018-07.
• Results first posted 2018-02-22.
• 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.

17. Record Summary

The registry describes a completed randomized factorial study of skin cancer prevention interventions, with enrollment of 197. The four listed groups are education control, motivational interviewing, UV-detect photographs, and the combination of photographs with motivational interviewing. Masking is listed as none.

The primary outcome is Sun Stage of Change at 3 months, a behavioral measure covering reported protection behavior and intentions across several stages. The study record lists a start of 2006-03 and primary completion of 2008-06. The broader description refers to a pilot study, a formal randomized efficacy trial, and a dismantling study.

The registry does not report primary outcome results, comparative estimates, statistical uncertainty, the analysis population, or detailed analysis methods. It also does not report participant flow or missing-data handling. The adverse-event fields record zero affected participants in each group, without an explanation of reporting procedures. Accordingly, the record describes the trial’s design and intended endpoint but does not provide enough outcome information to assess intervention effects.