Knowledge Evaluation and Assessment of the Effectiveness of an Education Intervention on Acne: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Knowledge Evaluation and Assessment of the Effectiveness of an Education Intervention on Acne (NCT01629797), a na na study. The primary outcome is Number of Correct Responses to Questionnaire Items Immediately Before and After and Educational Lecture.

2. Clinical Question

The study asks whether acne knowledge, as assessed by questionnaire, changes after an educational lecture and whether knowledge is retained at a later follow-up. It also describes an interest in comparing knowledge across ethnic groups and assessing psychosocial effects, but the posted results do not report findings for those questions.

This design can describe changes over time in the participating group, but it cannot by itself separate an effect of the lecture from other explanations for a change. The record does not report a randomized comparison, a concurrent untreated group, or a statistical estimate addressing those alternatives. Its stated aims include examining differences among ethnic groups and psychosocial effects; subgroup results and results for those other aspects are not reported in the registry record.

3. Trial Design

This is a completed, single-group study of an educational intervention for acne vulgaris. The registry lists Northwestern University as sponsor, planned enrollment of 100, and study dates from 2012-05 to primary completion in 2012-11. The phase and allocation are recorded as NA, and masking is recorded as NONE. The record describes an educational script on acne and teaching for patients with acne vulgaris.

The assessment sequence described in the registry begins with a questionnaire about acne knowledge and psychosocial effects before the educational intervention. Participants then complete a knowledge questionnaire immediately after the lecture. A phone call two months after the intervention is described for assessing retention of the educational material and quality of life related to psychosocial effects. The primary outcome concerns correct questionnaire responses immediately before and after the lecture; a secondary outcome concerns correct responses before and two months after an educational lecture.

Because this is a single-group design, the pre-intervention assessment serves as the reference point for the post-intervention assessment, rather than a separate control arm. The registry record does not report whether all participants completed each assessment, how questionnaires were scored beyond counting correct responses, or what statistical method was used to compare observations. Although the description mentions examination of knowledge across ethnic groups, the record does not report subgroup results. The study is marked completed, but completion status alone does not establish that every planned assessment or analysis is available in the posted results.

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

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 Number of Correct Responses to Questionnaire Items Immediately Before and After and Educational Lecture, measured over immediately before and after an educational lecture.

The primary endpoint is the number of correct responses to questionnaire items immediately before and immediately after an educational lecture about acne. It is intended to measure knowledge at two points around the teaching intervention. Counting correct responses focuses on answers that meet the questionnaire’s scoring criteria rather than on a general impression of whether participants learned something.

The before-and-after timing makes the outcome relevant to the study’s immediate educational question: whether questionnaire performance differs after the lecture in the group that received it. A count also allows the endpoint to retain information across questionnaire items, rather than reducing performance to a broad descriptive judgment. The registry record does not report the number of questionnaire items, their content, the scoring rules, or whether all items were weighted equally. Those details matter for interpreting the meaning and range of the count.

The registry identifies the unit as participants and describes calculating the number of correct responses at each assessment. It does not post the actual response counts, a summary of the change, or an inferential analysis. Therefore, the endpoint’s intended measurement is clear, but the posted results do not establish the size, precision, or statistical uncertainty of any change. The separate follow-up outcome concerns correct responses before and two months after the lecture; it is not a substitute for the primary immediate comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes repeated knowledge assessment in a single group, with the primary comparison made immediately before and after an educational lecture. It does not identify a statistical analysis method. The explanations below are general descriptions of methods that can be relevant to this kind of outcome; they should not be read as methods confirmed to have been used in this study.

What does a before-and-after comparison estimate?

In general, a within-person comparison uses observations from the same participant at different times. It can account for stable differences between participants because each person’s later observation is interpreted in relation to that person’s earlier observation. This structure is often analyzed with paired methods. The registry description indicates that participants completed questionnaires before and after the lecture, but it does not report whether the analysis retained participant-level pairing or how missing observations were handled.

A group-level pre/post contrast is not equivalent to a comparison against an untreated group. It describes the pattern over time in the observed group. Without a concurrent control condition, the contrast cannot isolate the intervention from other influences that may occur between assessments. This distinction concerns what the design can support, rather than a claim about the study’s unreported results.

What does a count outcome require?

The primary outcome is a count of correct questionnaire responses. In general, analysis of a count should reflect the count’s possible range and distribution. The number of items sets a natural limit, but the registry record does not report that number or the scoring details. A simple mean comparison may be easy to interpret, while a model for counts can make different assumptions about how observations vary. The choice depends on the data structure and the scientific question; no choice is reported.

In general, over-dispersion means that observed variation is greater than a simple model assumes. If a count model assumes less variation than the data contain, standard errors may be too small and confidence intervals may be too narrow. This can make inferential evidence appear more precise than it is. Whether over-dispersion is relevant to this questionnaire count cannot be determined from the registry record because the response data and model are not reported.

How should uncertainty be presented?

A point estimate describes the estimated outcome or contrast, while a confidence interval conveys its uncertainty under the chosen analysis. A p-value, when used, addresses compatibility between the data and a specified null hypothesis under model assumptions; it is not a measure of effect size or practical importance. In general, interpretation is strongest when an estimate and its uncertainty are considered together with the outcome’s meaning and the study design. No primary-outcome estimate, confidence interval, or p-value is reported in the registry record.

What is the role of the later assessment?

The record describes a phone assessment two months after the intervention to evaluate retention and psychosocial quality of life, and it lists a secondary outcome for correct responses before and two months after the lecture. In general, a later measurement addresses persistence over time, which is a different question from immediate change. The later contrast can also be affected by loss to follow-up or other changes over time. The record does not report follow-up completion, a retention estimate, or an analysis method for this outcome.

How should planning illustrations be distinguished from trial results?

The registry’s planning assumptions describe illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are planning assumptions, not evidence that this study used a two-arm design: the trial itself is described as single-group. Planning estimates are not observed power and do not replace an analysis of the observed data. The record does not report the trial’s own sample-size justification or any primary-outcome result from which a reader could assess such planning illustrations.

Overall, general statistical principles can clarify what kinds of analyses might be considered, but the registry record does not identify the method actually used. Without the analysis details and outcome results, readers cannot verify assumptions, reproduce an estimate, or evaluate the reported precision.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary immediate pre/post knowledge outcome and a secondary outcome concerning correct responses before and two months after the lecture. The study description also mentions psychosocial effects and possible differences in knowledge among ethnic groups. The posted record does not report results for these additional questions or explain how they were incorporated into an analysis plan.

Multiplicity arises when several outcomes, time points, or subgroup comparisons are examined. In general, considering many tests can increase the chance that at least one result appears unusual by chance. Statistical approaches can address multiplicity, but their choice depends on which comparisons were planned and which were considered primary. The registry record does not report a multiplicity strategy, a prespecified hierarchy of outcomes, or interim analyses. No such details should be inferred from the presence of multiple stated aims.

The registry lists no analyses. It does not report missing-data counts, reasons for missing assessments, or methods for handling missing responses. This matters because the number and characteristics of participants with observed scores can affect both the interpretation and precision of a repeated-assessment comparison. The record also does not specify an analysis population, such as whether analyses included everyone enrolled or only participants with completed questionnaires.

General methods for missing data make assumptions about why observations are absent and how missingness relates to observed or unobserved outcomes. Those assumptions cannot be assessed without reporting the amount and pattern of missingness and the analysis approach. The registry record does not report whether questionnaire items left unanswered were treated as incorrect, excluded, or handled by another rule. As a result, the scoring and analysis population cannot be reconstructed from the posted information.

These omissions do not show that missingness or multiplicity affected the study’s conclusions; no conclusions or analyses are posted for evaluation. They limit what can be independently assessed about the completeness and reliability of any potential outcome comparison.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The registry reports serious adverse event fields for the Acne Vulgaris group with 100 at risk and 0 affected. Its other adverse event fields also list 100 at risk and 0 affected. These are the posted event counts for the recorded categories; they should not be read as evidence that no event of any kind occurred.

The record does not list serious adverse event terms, and it does not give additional event descriptions. Deaths are not reported in the registry record; a missing death entry should not be interpreted as a reported count of zero. The adverse event summary does not explain the collection period, ascertainment procedures, or whether event reporting covered every participant throughout the study.

In general, an adverse event count is interpreted in the context of how events were defined, collected, and followed. A count of zero in a reported category indicates no events recorded in that category in the posted results, not certainty that the underlying risk is zero. These safety fields do not address the educational outcome and cannot establish the intervention’s effects on acne knowledge or psychosocial quality of life.

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

The registry record identifies a study designed to assess acne knowledge before and after an educational lecture, with a later assessment of retention and psychosocial quality of life. It also identifies the primary outcome as the number of correct questionnaire responses immediately before and after the lecture. These details establish what the investigators intended to measure, not what the measurements showed.

The posted record does not report a primary-outcome estimate, the underlying response data, or a statistical analysis. It therefore does not show whether knowledge scores rose, fell, or remained similar. It also does not quantify uncertainty, so the precision of any possible change cannot be judged. The absence of reported results is not evidence of no change, and it is not evidence of a change.

The single-group design can support description of observations over time among participants with data. It does not provide a concurrent counterfactual comparison. In general, changes after an educational session may reflect the session as well as repeated testing or other influences; the record does not report evidence that distinguishes among these explanations. No randomized comparison is described.

The study’s stated goals include examining knowledge across ethnic groups and understanding psychosocial effects. The registry does not report results for those aims, so it cannot establish whether knowledge differed across groups or whether psychosocial outcomes changed. Likewise, the later follow-up is described as part of the assessment plan, but its results are not posted.

The sound interpretation is limited: the registry documents a completed educational study and its planned outcome assessments, while leaving the outcome findings and analytical basis unreported. It does not support a conclusion about the direction or magnitude of change, its precision, or whether any observed change would be attributable to the educational intervention.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of how an outcome and a design define the questions that can be answered. A questionnaire administered before and after teaching can describe within-group changes in knowledge. The single-group structure, however, does not supply a separate control condition for distinguishing intervention-related change from other time-related influences. That distinction is central to interpreting a pre/post contrast.

The primary outcome is expressed as correct responses rather than as a broad subjective judgment. That gives the measurement a clear intended focus, but interpretation still depends on details such as questionnaire content, the number of items, scoring rules, and the way repeated responses are analyzed. Those details are not reported in the registry record. A reader cannot evaluate how well the count captures the intended knowledge construct without them.

The study also illustrates why outcome reporting matters. A completed study record and a clearly stated endpoint do not let readers assess an effect when estimates, uncertainty, and analysis details are absent. Without those elements, neither statistical significance nor practical importance can be evaluated. The same applies to the stated interests in follow-up retention, psychosocial effects, and differences among groups.

Finally, the record distinguishes a single-group educational study from the two-arm assumptions described for planning illustrations. Keeping trial design separate from planning scenarios avoids treating a hypothetical design as though it were the design actually conducted. The key statistical contribution of the record is therefore its documented question and measurement schedule; it does not provide the results needed to judge the observed outcome.

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 most important limitation for interpretation is that the registry record does not report the primary outcome results or any analyses. There is no posted estimate of pre/post change, no measure of uncertainty, and no reported test. The record therefore cannot support a statistical assessment of the intervention’s immediate association with questionnaire performance.

The single-group design lacks a separate control condition in the registry description. General causal interpretation is consequently limited: a change between assessments, if observed, could not automatically be attributed to the lecture. The record also does not describe random allocation or masking beyond listing masking as NONE and allocation as NA.

Measurement details are limited. The number and content of questionnaire items, scoring rules, treatment of unanswered items, and any evidence about measurement consistency are not reported in the registry record. Without these details, the meaning and comparability of the correct-response count are difficult to assess. The record does not report whether the same questionnaire was used at each time point.

The planned follow-up raises additional uncertainties because the registry does not report completion at the later assessment, missing-data handling, or retention results. It also does not report subgroup analyses for the stated interest in ethnic differences, or results for psychosocial outcomes. The analysis population and statistical methods are not reported, and no multiplicity approach is described.

Finally, planned enrollment of 100 does not establish how many participants contributed data to each outcome assessment. The registry does not report the outcome-specific denominators. The posted safety counts do not resolve these efficacy and reporting limitations.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Knowledge Evaluation and Assessment of the Effectiveness of an Education Intervention on Acne — NCT01629797.
• Registry record last updated 2013-06-20; status last verified 2013-04.
• Results first posted 2013-06-20.
• 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

NCT01629797 is a completed, single-group study sponsored by Northwestern University, with planned enrollment of 100 and study dates from 2012-05 to primary completion in 2012-11. Participants with acne vulgaris were described as receiving an educational script and teaching about acne.

The primary outcome was the number of correct questionnaire responses immediately before and after the lecture. A secondary outcome concerned correct responses before and two months after the lecture. The record also describes assessing psychosocial effects and knowledge across ethnic groups.

The registry record does not report outcome results, statistical analyses, missing-data handling, or subgroup findings. Safety fields list 0 serious adverse events and 0 other adverse events among 100 at risk; deaths are not reported in the registry record. The posted information establishes the study’s aims and assessment schedule but does not quantify an outcome change or its precision.