Health Focused Motivational Treatment for Alcohol Dependent Veterans: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Health Focused Motivational Treatment for Alcohol Dependent Veterans (NCT00252590), a randomized na study. The primary outcome is Percentage of Days Abstinent From Alcohol.

2. Clinical Question

3. Trial Design

The registry describes a randomized, parallel-group behavioral trial with no masking. The three arms were Health Motivational Feedback, Health Education, and Control - Treatment as Usual. The descriptions distinguish personalized health-related feedback from non-personalized didactic health-related education; the control is described as having no added treatment.

The registry records enrollment of 99. The outcome results list 33 participants for Health Motivational Feedback, 28 for Health Education, and 31 for Control - Treatment as Usual. These are the group counts attached to the posted primary outcome summaries; the registry record does not explain how they relate to the enrollment figure or describe the flow of participants through the study.

The study began in 2005-11, reached primary completion in 2009-05, and is marked completed. Its listed phase is NA. The sponsor is the VA Office of Research and Development. The primary outcome was assessed at 4 months. The registry also lists percentage of days abstinent from all substances as a secondary outcome, also at 4 months.

The registry record does not report the allocation procedure beyond identifying the study as randomized, or provide details of the sequence generation, concealment, or implementation. It does not report whether the interventions were delivered in addition to particular components of outpatient treatment. These details should not be inferred from the arm labels.

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 Percentage of Days Abstinent From Alcohol, measured over 4 months.

The primary endpoint is the percentage of days abstinent from alcohol, measured at 4 months and summarized as a mean with a standard deviation. It expresses abstinence over the assessment period as a percentage of days rather than as a count of drinks or a measure of alcohol-related harm. The registry does not specify the exact assessment window, measurement instrument, or method used to determine abstinence.

As a continuous outcome, the endpoint can be summarized by the group mean and the spread of individual observations around that mean. The mean gives a central measure of the reported abstinence percentages; the standard deviation describes how much those observations vary within a group. Neither summary alone shows the full distribution or how many participants had particular patterns of abstinence.

Comparing this endpoint across randomized groups addresses whether the recorded average percentage of abstinent days differed between the intervention arms and treatment as usual at the stated assessment. It is a measure of alcohol abstinence, not the listed secondary outcome of abstinence from all substances. The registry record does not report a clinically important difference threshold or explain how the primary endpoint was selected.

7. Results Posted in the Registry

• Health Motivational Feedback: mean 91.40 versus 83.00 on control; difference 8.40 (95% CI -2.21 to 19.01), standardized effect d = 0.40; z-test p = 0.121.
• Health Education: mean 87.30 versus 83.00 on control; difference 4.30 (95% CI -8.56 to 17.16), standardized effect d = 0.17; z-test p = 0.512.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Percentage of Days Abstinent From All Substances

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Health Motivational Feedback: mean 91.20 versus 82.10 on control; difference 9.10 (95% CI -1.47 to 19.67), standardized effect d = 0.43; z-test p = 0.092.
  • Health Education: mean 84.10 versus 82.10 on control; difference 2.00 (95% CI -11.94 to 15.94), standardized effect d = 0.07; z-test p = 0.779.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Health Motivational Feedback and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Health Education and the control. The interval gives the range of effects that remain compatible with the data.

The secondary endpoint is the percentage of days abstinent from all substances at 4 months. Its observed means follow a pattern broadly similar to the primary endpoint: the Health Motivational Feedback group has the highest posted mean, followed by Health Education and then treatment as usual. The recalculated comparisons likewise point to positive mean differences for both intervention groups relative to control, but their confidence intervals include zero. No sponsor-reported analysis is posted for this secondary outcome.

This parallel descriptive pattern is relevant context, but it does not independently confirm the primary finding. The endpoints are related measures of abstinence, and their results should not be treated as independent replications. The secondary endpoint covers all substances, while the primary endpoint is specifically abstinence from alcohol. A difference in the measured scope also means that the two outcomes are not interchangeable.

Unadjusted secondary results carry less weight because they may be among multiple outcomes or comparisons examined, and the registry record does not report a multiplicity strategy or a prespecified hierarchy for interpreting them. In general, examining multiple outcomes increases the chance that some results appear notable through random variation alone unless the analysis accounts for that process. The record lists two outcome measures but does not describe how secondary findings were intended to influence conclusions.

The secondary results can therefore be read as descriptive and exploratory context for the primary comparison, not as a separate basis for a definitive claim. The registry does not report whether missingness, outcome measurement, or analysis populations differed between the primary and secondary endpoints.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Percentage of Days Abstinent From All Substances

9. Statistical Interpretation

10. Statistical Methods Explained

Randomization is intended to make the comparison groups similar, on average, with respect to factors that could affect the outcome. In a randomized trial, differences in outcomes can therefore be examined as comparisons between assigned groups, subject to issues such as departures from assignment, missing observations, and how outcomes are measured. The registry identifies this study as randomized, but details of the randomization procedure and analysis populations are not reported in the registry record.

What does the reported ANOVA test?

The sponsor-reported method is ANOVA, with p = 0.32 for the three groups. In general, ANOVA tests whether the group means show evidence of an overall difference; it does not, by itself, specify which pair of groups might differ or the size of any particular contrast. The registry record provides no ANOVA estimate, confidence interval, degrees of freedom, model specification, or further explanation of the test. The reported p-value should therefore be read as the posted overall test result, not as a pairwise estimate.

What do the pairwise recalculations represent?

The posted recalculations compare each intervention arm with treatment as usual using unadjusted differences between the reported means. The estimated mean differences are 8.4 for Health Motivational Feedback and 4.3 for Health Education. These are simple, unadjusted re-calculations from the group summaries, rather than reported adjusted model estimates. The associated confidence intervals and p-values are also unadjusted. No discrepancy is flagged between the posted summaries and these recalculations.

Unadjusted means that the recalculations do not account for other variables or any adjustment procedure. The registry record does not report whether the sponsor’s ANOVA adjusted for covariates, whether there were prespecified pairwise contrasts, or whether any other model-based estimates were produced. Because an overall ANOVA and pairwise comparisons answer different questions, their p-values need not match and should not be interpreted as competing estimates of the same test.

Why does variability matter?

The outcome is continuous and is reported as a mean and standard deviation. The standard deviation describes variation among the observed outcome values within a group; it is not the uncertainty in the estimated group mean. The standard error instead represents the estimated sampling variability of a mean. In general, greater variation among observations makes a group mean less precisely estimated when other features are held fixed. The posted group spreads and standard errors reflect the observed summaries, but the registry record does not report distributional diagnostics or details of any assumption checks.

For continuous outcomes, methods that compare means are generally most straightforward to interpret when the measurement and analysis are appropriate for the data distribution and study design. The registry lists ANOVA but does not state whether assumptions were assessed, whether transformations or robust methods were considered, or how any departures were handled. Those procedures cannot be inferred from the outcome summaries.

What can a p-value tell the reader?

In general, a p-value measures how incompatible the observed data are with a specified statistical null model, assuming that model and its assumptions hold. It is not the probability that the null hypothesis is true, and it does not quantify the size or importance of a difference. Here, p = 0.32 is the reported overall ANOVA result. The recalculated pairwise p-values, 0.121 and 0.512, relate to their respective unadjusted comparisons. They should be interpreted alongside the estimated differences and confidence intervals rather than on their own.

The registry record does not report a statistical analysis plan, a prespecified significance threshold for the sponsor analysis, handling of multiple comparisons, or interim analyses. The planning illustration uses a two-sided significance level of 0.05, but that assumption belongs to the illustration and does not establish the original trial’s design or analysis choices.

What do the sample-size illustrations mean?

The planning calculations use the observed effect as a starting point and consider smaller fractions of that effect. They are not results from participants in the trial and do not describe the trial’s achieved power. General power calculations estimate how often a planned analysis might detect an assumed effect under specified design and statistical assumptions. They depend on those assumptions; they do not guarantee a result or correct uncertainty in the observed estimate. The registry record does not report the original sample-size justification or its assumptions.

11. Confidence Intervals and Precision

The 95% confidence interval for the recalculated mean difference between Health Motivational Feedback and treatment as usual runs from -2.205 to 19.01. For Health Education compared with treatment as usual, it runs from -8.561 to 17.16. In both cases, the interval includes zero, the value corresponding to no difference in group means. Each interval also includes positive differences, so the point estimate should not be mistaken for a precisely established effect.

In general, a confidence interval gives a range of values compatible with the data under the method used. Its width conveys precision: a wider interval leaves more uncertainty about the size and direction of the difference. These intervals are unadjusted recalculations from the posted summary statistics, not sponsor-reported confidence intervals. They do not account for any unreported adjustment or multiplicity procedure.

The group standard deviations are 14.2 for Health Motivational Feedback, 23.6 for Health Education, and 26.8 for treatment as usual. The variability in the observed scores contributes to uncertainty in comparisons, along with the group counts and the analysis method. The registry record does not report confidence intervals for the individual group means or explain missing outcome data.

Precision is distinct from whether a finding crosses a chosen statistical threshold. A confidence interval can be used to see which effect sizes remain compatible with the observed summaries, but it does not establish that all values inside it are equally likely or that values outside it are impossible. The intervals are not evidence of equivalence, and the registry record does not state an equivalence or non-inferiority objective.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for 80% power and participants per arm for 90% power. They are not total event counts. The registry’s planning assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. The original trial’s own design assumptions and sample-size justification are not reported in the registry record.

The 80% power column describes the planned group size under which the calculation would have an 80% chance of detecting the assumed effect at the stated significance level, if the assumptions hold. The 90% power column uses a higher target chance of detection and consequently requires more participants per arm under the same conditions. These are planning illustrations based on the observed effect, not observed power.

Rows for planning for 75% or 50% of the observed effect posit smaller differences than the row for 100% of the observed effect. Smaller effects are harder to distinguish from random variation, so the corresponding calculations require more participants per arm. For example, the primary comparison of Health Motivational Feedback with treatment as usual lists 101 participants per arm for 80% power when planning for 100% of the observed effect, and 402 participants per arm when planning for 50% of that effect. The calculations are illustrative rather than predictions of what a future study would find.

The estimates are specific to the stated assumptions and the observed effect used as their starting point. They should not be read as validation of the original design or as evidence that the trial was adequately or inadequately sized. Different planning assumptions, outcome variability, allocation, or analysis choices could lead to different requirements.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 8.400; pooled standard deviation σ = 21.251.
2. n = 2 × (1.96 + 0.842)² × 21.251² / 8.400² = 100.5, rounded up to 101 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 8.40000000000001                      # observed difference in means
sigma <- 21.251064489467                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(252590)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 101 (80% power), 135 (90% power)
 75% of observed effect: n per arm = 179 (80% power), 240 (90% power)
 50% of observed effect: n per arm = 402 (80% power), 539 (90% power)
power.t.test: 101.4 
Simulated power at n = 101 per arm: 0.797 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports the sponsor’s analysis as an ANOVA across Health Motivational Feedback, Health Education, and treatment as usual, with p = 0.32. It does not post an estimate, confidence interval, or further model details for that analysis. The recalculations compare each intervention separately with treatment as usual using the posted group means and standard deviations; they are unadjusted pairwise comparisons, not a reproduction of the overall ANOVA.

No discrepancy is flagged between the posted summaries and the recalculations. Even so, the reported ANOVA and pairwise calculations answer different statistical questions. The overall test addresses evidence of differences among the three group means collectively, whereas each recalculation estimates a particular intervention-control mean difference. Their p-values are not directly interchangeable, and the recalculated pairwise results do not replace the sponsor-reported analysis.

The record does not explain whether the ANOVA was prespecified, adjusted, or followed by additional comparisons. Nor does it report the sponsor’s analysis plan or any interpretation beyond the posted result. The clearest reading is to retain the sponsor’s reported overall result as the registry analysis and regard the pairwise estimates as supplementary, unadjusted recalculations from the available summaries.

15. Multiplicity, Missing Data and Analysis Populations

The registry record identifies one reported analysis: an ANOVA across the three groups for the primary endpoint. It also lists a secondary outcome, but no sponsor-reported analysis is posted for that outcome. The record does not report whether there were additional planned outcomes, tests, subgroup analyses, or pairwise comparisons, nor whether a multiplicity adjustment or outcome hierarchy was used.

In general, multiplicity matters when several statistical tests are interpreted together. The more tests considered, the greater the opportunity for at least one result to appear unusual by chance. Adjustment methods or a prespecified hierarchy can help define how evidence is interpreted across tests. Neither the method nor the prespecification details are reported in the registry record. The unadjusted pairwise recalculations should therefore be understood as separate comparisons, not as multiplicity-adjusted findings.

Information about missing data is also not reported in the registry record. It does not explain whether all randomized participants contributed primary outcome data, how unavailable measurements were handled, or whether any imputation or sensitivity analysis was used. The outcome summaries have group counts, but those counts alone do not establish why observations may be absent or what population was analyzed.

The analysis population is not reported in the registry record. Although the study is identified as randomized, the record does not state whether analyses followed randomized assignment, included only participants who completed treatment, or used another population definition. It also does not provide a participant flow account or identify deviations from assigned intervention. These absences limit assessment of possible bias and make it important to distinguish registry outcome summaries from a full account of trial conduct and analysis.

16. 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.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: inpatient psychiatric hospital admission (2.9%).

The registry lists serious adverse events for safety populations of 35 in Health Motivational Feedback, 30 in Health Education, and 34 in treatment as usual. Serious adverse events affected 1 participant in Health Motivational Feedback and 0 in each of the other groups. The record lists inpatient psychiatric hospital admission as a serious-event term at 2.9%. It does not provide further detail in the posted safety details about timing, relatedness, or event-level descriptions.

Other adverse events affected 0 participants in each listed group. Death counts are not reported in the registry record. These summaries describe what was recorded in the safety fields; zero recorded events should not be interpreted as proof that no events of any kind occurred. The safety group counts differ from the counts attached to the primary outcome summaries, and the registry record does not explain the difference.

These figures are descriptive and do not establish comparative safety. The registry does not report a statistical comparison of adverse events or explain how events were collected and classified.

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

The posted results show higher mean percentages of days abstinent from alcohol in both behavioral intervention groups than in treatment as usual at 4 months. The unadjusted recalculated mean differences are positive, but their confidence intervals include zero and span a range of possible differences. The sponsor’s overall ANOVA has p = 0.32. Taken together, these findings do not provide clear statistical evidence of differences among the groups in the posted analysis.

This does not establish that the groups are equivalent, nor does it prove that either intervention has no effect. An estimate that is uncertain can be compatible with more than one explanation. The registry does not report an equivalence margin, a non-inferiority objective, or a clinically important difference threshold. Statistical uncertainty should not be converted into a categorical claim about the interventions.

The results also do not show that every participant followed the group average. The standard deviations indicate variation in observed outcomes, and the record does not supply individual-level results, distributions, or details about how abstinence was measured. The primary endpoint concerns the percentage of days abstinent from alcohol; it does not directly summarize other aspects of health, treatment engagement, or substance-related harm.

The secondary endpoint considers abstinence from all substances, but its results are not a substitute for the primary endpoint and lack a posted sponsor analysis. The registry record also does not report missing-data handling, analysis populations, or a full statistical plan. These limitations mean that the posted summaries are best interpreted as an account of the available registry results, rather than as a complete evaluation of every relevant clinical or statistical question.

18. Why This Trial Matters Statistically

This trial is statistically informative because it illustrates the distinction between observed group means and evidence about differences between groups. The intervention groups have higher posted primary-outcome means than treatment as usual, but the pairwise confidence intervals include zero, while the sponsor-reported overall ANOVA has p = 0.32. A direction in the descriptive summaries is not enough to establish a precise or dependable difference.

The record also provides a useful example of how analyses at different levels answer different questions. ANOVA is an overall comparison across the three groups, while the recalculations estimate two specific intervention-control contrasts. Keeping those questions separate prevents an overall p-value from being mistaken for an effect estimate and prevents unadjusted recalculations from being presented as the sponsor’s model.

Precision matters alongside the point estimates. The intervals permit a broad range of values, and planning illustrations show how required group sizes depend on the assumed effect. A design based on a smaller target effect requires more participants per arm under the stated planning assumptions. Those illustrations are not evidence about the trial’s original rationale or its observed power.

Finally, the registry’s limits are part of the statistical interpretation. The absence of information about missing outcomes, analysis populations, multiplicity, and the original sample-size rationale constrains what can be inferred from the posted results. Transparent recognition of those gaps is essential when translating registry summaries into conclusions.

19. 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.

Important details for evaluating the trial are not reported in the registry record. These include the randomization procedure, allocation concealment, intervention delivery and adherence, outcome measurement instrument, and exact assessment window for the 4-month endpoint. The record also does not explain the relationship between enrollment of 99 and the group counts attached to outcome summaries.

The analysis population and missing-data procedures are not reported. Without participant flow and outcome availability details, it is not possible to determine from the registry summaries why the reported group counts differ from enrollment or whether missingness could affect comparisons. The record does not describe departures from assigned intervention, treatment exposure, or follow-up beyond the stated endpoint timeframe.

The sponsor-reported result is an overall ANOVA, without a posted estimate or confidence interval. The recalculated pairwise comparisons are unadjusted, and no multiplicity strategy is reported. Model details, assumption checks, covariate adjustments, sensitivity analyses, and the original statistical analysis plan are also not reported in the registry record.

The primary outcome is a mean percentage of abstinent days, but the registry does not give a clinically important difference threshold or the instrument used to obtain the measure. The secondary outcome has no sponsor-reported analysis in the record. Safety reporting is limited to the posted group counts and event term; deaths are not reported in the registry record, and event relatedness and collection procedures are not described. These gaps make the registry results informative but incomplete.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Health Focused Motivational Treatment for Alcohol Dependent Veterans — NCT00252590.
• Registry record last updated 2016-03-21; status last verified 2016-02.
• Results first posted 2016-03-21.
• 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.

23. Record Summary

NCT00252590 is a completed randomized, unmasked, parallel-group behavioral study sponsored by the VA Office of Research and Development. Enrollment is listed as 99. The study began in 2005-11 and reached primary completion in 2009-05.

The three groups were Health Motivational Feedback, Health Education, and Control - Treatment as Usual. The primary endpoint was mean percentage of days abstinent from alcohol at 4 months. The sponsor-reported ANOVA across groups has p = 0.32. Unadjusted recalculations compare each intervention with treatment as usual; both estimated differences are positive, and both confidence intervals include zero.

The registry also lists percentage of days abstinent from all substances as a secondary outcome. The record does not report a sponsor analysis for that outcome, the original sample-size rationale, or key details of missing-data handling, analysis populations, and multiplicity procedures.