Alcohol & Mobile Phone Study to Reduce High-risk Alcohol Use and Consequences: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Alcohol & Mobile Phone Study to Reduce High-risk Alcohol Use and Consequences (NCT04213846), a randomized na study. The primary outcome is Daily Drinking Questionnaire - Typical Number of Drinks Per Week.

2. Clinical Question

3. Trial Design

The study, NCT04213846, is listed as a completed randomized, parallel-group trial sponsored by the University of Washington. The registry record lists enrollment as 408. It gives a start date of 2020-01-06 and a primary completion date of 2022-04-29. The study is listed as not having a masking procedure, and its phase is recorded as NA.

Participants were assigned to a mobile alcohol expectancy intervention or an assessment-only control. The intervention combined app-based assessments with personalized messaging and access to alcohol-related psycho-educational information. The study description specifies two brief surveys per day and two intervention messages per day for three weeks. The control group received assessments but no intervention. The registry describes the intended population as young adult college students.

The primary outcome was the Daily Drinking Questionnaire measure of typical drinks per week. It was scheduled for assessment at baseline, 1-month follow-up, 6-month follow-up, and 12-month follow-up. The record also lists Alcohol Use Disorder Identification Test Total Score as a secondary outcome, and records 5 outcome measures and 13 analyses. The specific results and analysis details for those measures are not reported in the registry record.

Randomization can support a comparison of assigned groups, but the registry information alone does not show how assignment was generated, whether allocation was concealed, or how the analysis handled departures from assigned treatment. Those details are not reported in the registry record. The record also does not give a detailed statistical analysis plan or explain the rationale for the enrollment target.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Difference in number analyzed by condition are due to differences in follow-up participation rates and/or items skipped by participants.

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 Daily Drinking Questionnaire - Typical Number of Drinks Per Week, measured over Baseline, 1-month follow-up, 6-month follow-up, and 12-month follow-up.

The primary endpoint is the Daily Drinking Questionnaire’s measure of typical drinks consumed per week during the past month. It is a continuous outcome reported as a mean with standard deviation, and its unit is drinks. The measure was scheduled at baseline and at 1-month, 6-month, and 12-month follow-up.

In general, a measure of typical weekly consumption offers a direct summary of reported drinking volume over a defined recall period. A continuous outcome can retain differences across participants rather than reducing drinking to a simple category. The mean describes the group’s average reported level, while the standard deviation describes how spread out participant values are around that average. These summaries answer different questions: one concerns the typical level, and the other concerns variability among participants.

The measure is self-reported, so it reflects participants’ reports rather than an independently verified count. The registry record does not describe additional measurement procedures or validation in this trial. It also does not report the primary endpoint values or between-condition estimates at any of the listed assessment times. As a result, the measurement plan is clear, but the magnitude and precision of the observed outcome differences cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The trial is described as randomized and parallel-group. In general, random assignment aims to make the comparison groups similar, on average, with respect to factors measured and unmeasured at the start of a trial. A parallel-group design assigns participants to a condition and follows those groups over time. Randomization can strengthen a causal interpretation when assignment and follow-up are handled appropriately, but the label alone does not establish that groups remained comparable in the analyzed data. The registry record does not describe the randomization procedure or allocation concealment.

The primary outcome is continuous, and the registry identifies the reported summary as a mean with standard deviation. A mean is the arithmetic average of participant values. A standard deviation describes the spread of those values around the mean; it is not the uncertainty in the mean itself. In general, the standard error and a confidence interval are used to describe uncertainty in an estimated mean or difference. The registry record does not report the primary outcome summaries, uncertainty intervals, or method used to estimate a between-condition contrast.

Repeated assessment creates a statistical choice: investigators may compare groups separately at each follow-up, model measurements jointly over time, or use another prespecified approach. These approaches can answer related but not identical questions. A joint longitudinal model, for example, can account for the correlation between measurements from the same participant, while separate comparisons treat each time point as its own contrast. The statistical analysis plan, model specification, and treatment of baseline values are not reported in the registry record. It is therefore not possible to identify which estimand or model underlies any primary outcome result.

In general, an estimand states precisely what treatment effect is being targeted, for which participants, under what handling of events such as non-adherence or missing outcomes, and how the outcome is summarized. Clarifying the estimand helps readers distinguish a comparison based on assigned condition from one based on intervention received or measurements available. The registry record identifies the assigned conditions and outcome schedule, but it does not provide those further details.

The record notes that analyzed numbers by condition differ because of follow-up participation and/or items skipped by participants. Missing outcome data can reduce precision. It can also introduce bias when the reasons for missingness are related to the outcome, especially if those reasons differ between conditions. In general, complete-case analysis, imputation, and likelihood-based models rely on different assumptions and may produce different estimates. The record does not state which missing-data method was used, describe the pattern of missingness, or report sensitivity analyses. Without those details, the robustness of any estimate to missing data cannot be assessed.

The record lists 13 analyses. A larger set of analyses can involve multiple outcomes, time points, or contrasts. In general, when many hypotheses are tested, the chance of at least one apparently unusual result can increase unless the analysis plan accounts for multiplicity. Whether and how the analyses were prioritized or adjusted is not reported in the registry record. The primary outcome itself has several time points, and the record does not reduce it to one comparison. That makes the choice of primary contrast important for interpretation.

The record’s sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. For outcomes other than time-to-event outcomes, the illustration is described in participants per arm, and the assumed effect is a stated fraction of the observed effect. Such an illustration is a planning exercise, not an observed result or an observed-power calculation. The effect estimates needed to assess the illustration are not reported in the registry record, and the record does not report the trial’s own sample-size justification. It is therefore not possible to judge whether the illustration matches the original design rationale.

In general, over-dispersion means that observed variation is greater than a model assumes. When present, a model that understates variability may report uncertainty that is too small. This concept is most directly relevant to outcomes whose variance structure is modeled, and it should not be presumed to apply to this continuous endpoint. The registry record does not report a model or a diagnostic assessment that would permit a trial-specific discussion of over-dispersion.

Finally, statistical significance and magnitude are distinct. A small estimate may be precise, while a larger estimate may be uncertain; either can occur depending on the data and analysis. Interpreting the primary endpoint requires the actual estimate and its uncertainty, alongside the analysis method and missing-data handling. Those outcome results and methods are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 5 outcome measures and 13 analyses. The primary outcome is measured at baseline, 1-month follow-up, 6-month follow-up, and 12-month follow-up, and the record notes that it has several categories or time points rather than one reduced comparison. If multiple outcomes, time points, or contrasts are examined, multiplicity is relevant: repeated testing can increase the chance of observing an apparently notable result by chance. In general, investigators can address this through prespecified primary contrasts, adjustment procedures, or careful interpretation of exploratory results. The registry record does not state whether any such approach was planned or used.

The record identifies Alcohol Use Disorder Identification Test Total Score as a secondary outcome, but does not provide its result or analysis details. It also does not identify which analyses were primary, secondary, or exploratory beyond the stated primary outcome and secondary measure. No correction for multiple comparisons is reported in the registry record, so it is not possible to determine how multiplicity was handled.

The record says that the number analyzed by condition varied because of differences in follow-up participation and/or items skipped by participants. Thus, enrollment does not establish how many participants contributed outcome data at each time point. The analyzed counts, reasons for missingness, and missing-data method are not reported in the registry record. In general, missingness can affect precision and, depending on its relationship to outcomes and condition, can also affect the validity of a comparison.

The record does not specify the analysis population, such as whether participants were analyzed according to randomized assignment, nor does it describe exclusions or sensitivity analyses. These omissions limit assessment of how closely the reported analysis, if results were available, would preserve the randomized comparison.

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 lists serious adverse event figures separately for the assessment-only control and the mobile alcohol expectancy intervention. For the assessment-only control, 203 participants were at risk for serious adverse events, and 0 were affected. For the intervention, 205 participants were at risk, and 0 were affected. Deaths are listed as 0 in both groups. The record lists 0 other adverse events in each group. No top serious adverse event terms are listed.

These entries describe the events recorded in the registry, not a complete assessment of every possible adverse experience. A zero in the serious-event field means that no affected participants are recorded in that category; it does not establish that no unrecorded or unreported events occurred. The registry record does not give additional detail about event definitions, ascertainment procedures, severity grading, or follow-up for safety reporting.

Safety comparisons also depend on the duration and completeness of monitoring and on how events were sought and classified. Those details are not reported in the registry record. The displayed figures should therefore be read as the registry’s recorded serious-event counts, rather than as proof that the intervention has no safety concerns.

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

The record establishes that a randomized, parallel-group study compared a mobile alcohol expectancy intervention with an assessment-only control among young adult college students. It describes the app-based intervention, the follow-up schedule, and the primary measure of typical drinks per week. It also records enrollment as 408 and lists the study as completed.

Those design details do not establish what happened to the primary outcome. Numerical outcome results are not reported in the registry record. There is no basis in the recorded information to state whether the intervention group’s mean was higher or lower at follow-up, how large any difference was, or how precise an estimate might be. The absence of a reported estimate is not evidence that the groups were equal, and completion status is not evidence of a particular finding.

Even when an effect estimate is available, its interpretation depends on the contrast, analysis population, handling of baseline measurements, and missing-data assumptions. The registry record does not report those methodological details. It notes that the number analyzed varied between conditions because of follow-up participation and/or skipped items, which makes the analyzed population especially important to understand.

The recorded serious adverse event figures show 0 affected participants in each condition, with 0 deaths listed in each. Those registry entries are limited to the recorded categories and do not establish the absence of every possible adverse experience.

The appropriate reading is therefore descriptive rather than conclusive: the study design and outcome plan are documented, but the primary outcome findings needed to characterize an intervention effect are not reported in the registry record. A clinical or practical conclusion about the intervention cannot be drawn from the information recorded.

13. Why This Trial Matters Statistically

This trial is statistically notable for combining repeated mobile assessment with personalized intervention messaging. The primary endpoint was intended to capture typical weekly drinking across several follow-up points, while the intervention description emphasizes links between participants’ expectations, experiences, alcohol use, and consequences. This design makes the definition of the main comparison important: a result at one follow-up may answer a different question from a pattern across all follow-ups.

The record also highlights a common issue in longitudinal clinical research: the number analyzed can differ from the number enrolled because participants do not complete every follow-up or skip questionnaire items. The registry explicitly attributes differences in analyzed numbers by condition to follow-up participation and/or skipped items. This makes transparent reporting of outcome counts, missing-data patterns, and analysis assumptions essential for evaluating the strength of a comparison.

The study has a randomized parallel-group design, but the registry record does not report the detailed statistical plan or primary outcome estimates. As a result, readers cannot assess the precision of the intervention comparison, the handling of repeated measurements, or the way multiple analyses were interpreted. The record lists 13 analyses and 5 outcome measures, adding importance to clear prespecification and distinction between primary and secondary questions.

The serious adverse event entries are also interpretable only in context: they record zero affected participants in each group, but the registry does not describe the full event ascertainment process. More broadly, this study illustrates the difference between a documented trial design and a complete statistical report. For evidence assessment, the intervention description and randomization are not substitutes for estimates, uncertainty intervals, and transparent analysis details.

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 consequential limitation of the registry information is that it does not report numerical results for the primary outcome. Means, standard deviations, between-condition estimates, and uncertainty measures are absent, so the observed difference and its precision cannot be evaluated. The record’s completed status does not fill this gap.

The record identifies several primary outcome time points but does not specify the primary contrast or analysis model. It does not state whether follow-up comparisons were adjusted for baseline, whether measurements were analyzed jointly over time, or how within-participant correlation was addressed. The analysis population and treatment of participants who did not complete follow-up are also not reported.

Different analyzed numbers by condition are attributed to follow-up participation and/or skipped items. The registry record does not give the number analyzed at each time point, the amount or pattern of missingness, or the assumptions and methods used to address it. Without these details, it is not possible to assess whether missing outcomes affected precision or may have introduced bias.

The record lists 5 outcome measures and 13 analyses but does not describe the multiplicity strategy or identify the full set of prespecified contrasts. It also does not report the trial’s own sample-size justification, detailed randomization procedures, or statistical analysis plan. The sample-size assumptions described for planning do not replace those design details.

Finally, the primary outcome is self-reported typical drinks per week. The registry describes what it measures but does not provide trial-specific information about measurement quality or corroboration. The serious adverse event entries are limited to recorded counts, with event ascertainment details not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Alcohol & Mobile Phone Study to Reduce High-risk Alcohol Use and Consequences — NCT04213846.
• Registry record last updated 2024-09-26; status last verified 2024-09.
• Results first posted 2024-09-26.
• 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

NCT04213846 is a completed randomized, parallel-group study sponsored by the University of Washington. The registry lists enrollment as 408 and describes a mobile alcohol expectancy intervention for young adult college students, compared with an assessment-only control. The intervention involved twice daily messages for three weeks and access to psycho-educational alcohol information.

The primary outcome was typical self-reported drinks per week, measured at baseline and at 1-month, 6-month, and 12-month follow-up. Alcohol Use Disorder Identification Test Total Score was listed as a secondary outcome. The record lists 5 outcome measures and 13 analyses, and notes that analyzed numbers differed by condition because of follow-up participation and/or skipped items.

Serious adverse event figures list 0 affected participants in each condition and 0 deaths in each. Numerical primary outcome results, detailed analysis methods, and missing-data procedures are not reported in the registry record.