One-Day Life Skills Workshop for Veterans With TBI, Pain and Psychopathology: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for One-Day Life Skills Workshop for Veterans With TBI, Pain and Psychopathology (NCT02844946), a randomized na study. The primary outcome is World Health Organization-Quality of Life (WHO-QOL).

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group study of a one-day life skills workshop for veterans with mild traumatic brain injury, distress-based psychopathology, and chronic pain. The intervention was called ACT on Life and was based on Acceptance and Commitment Therapy. The comparator was treatment as usual, described as continued usual care. The identity of the masked party and the procedures used to maintain masking are not reported in the registry record.

The registry lists an enrollment of 39 and a completed study. It gives a start date of 2016-10-03 and a primary completion date of 2018-09-03. For the primary outcome, the record states that 27 participants were assigned to ACT on Life, but only 19 were eligible, had valid data, and actually began the workshop. The posted ACT on Life outcome summary includes 19 participants; the treatment-as-usual summary includes 12. The record does not explain the difference between assignment and the ACT on Life outcome group, nor does it give further detail on the treatment-as-usual analysis population.

The outcome timeframe is through study completion, an average of 3 months following workshop attendance. Details of the randomization process, allocation concealment, sites, recruitment criteria, and the original statistical plan are not reported in the registry record. The registry lists a primary outcome and three secondary outcomes, while other outcome-measure details are not reported in the registry record. These limits matter when judging how broadly the posted summaries represent the people randomized and the study's prespecified questions.

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: 27 participants were assigned to the ACT on Life Condition. Only 19 were eligible, with valid data, and actually began the workshop.

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.

Population: Of note, initially 27 participants were assigned to the ACT on Life Condition. However, only 19 of those were eligible, with valid data, and actually began the workshop.

6. Primary Endpoint

The registry lists the primary outcome as World Health Organization-Quality of Life (WHO-QOL), measured over Through study completion, an average of 3 months following workshop attendance.

The primary outcome was the World Health Organization-Quality of Life (WHO-QOL) measure. Its general Quality of Life scale uses two items addressing overall quality of life and general health. Each item is scored from 1 to 5, giving the scale a stated range of 2 to 10; higher scores represent higher quality of life. The measure therefore captures a broad self-reported assessment rather than a direct measure of one specific symptom or diagnosis.

The registry reports group means in scale units with standard errors. The measurement timeframe was through study completion, an average of 3 months following workshop attendance. The choice of a broad quality-of-life outcome fits the stated aim of a unified workshop for veterans dealing with multiple, interconnected concerns. It can describe participants' overall appraisal across quality of life and general health, but it does not by itself show which elements of the workshop, care, or participants' circumstances might account for a group difference. The registry record does not report a more detailed rationale for selecting this measure, nor does it describe the timing of individual assessments beyond the stated timeframe.

7. Results Posted in the Registry

• ACT on Life: mean 6.11 versus 5.20 on control; difference 0.91 (95% CI -3.96 to 5.78), standardized effect d = 0.12; z-test p = 0.714.

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.

Military to Civilian Questionnaire (M2C-Q)

• 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 errors.
• Result:
  • ACT on Life: mean 1.81 versus 2.14 on control; difference -0.33 (95% CI -1.06 to 0.40), standardized effect d = -0.33; z-test p = 0.375.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between ACT on Life and the control. The interval gives the range of effects that remain compatible with the data.

PTSD Checklist-Civilian Version (PCL-C)

• 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 errors.
• Result:
  • ACT on Life: mean 49.20 versus 54.40 on control; difference -5.20 (95% CI -17.20 to 6.80), standardized effect d = -0.31; z-test p = 0.396.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between ACT on Life and the control. The interval gives the range of effects that remain compatible with the data.

Acceptance and Action Questionnaire-II (AAQ-II)

• 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 errors.
• Result:
  • ACT on Life: mean 22.80 versus 30.30 on control; difference -7.50 (95% CI -16.75 to 1.75), standardized effect d = -0.60; z-test p = 0.112.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between ACT on Life and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcomes cover military-to-civilian adjustment, post-traumatic stress symptoms, and psychological flexibility or acceptance-related functioning. For all three, the estimated group differences are in the same numerical direction when expressed as ACT on Life minus treatment as usual. However, the scales measure different constructs, and the meaning of a higher or lower score depends on the scoring of each measure. A shared direction in the estimates does not make the outcomes interchangeable or establish a consistent effect across all domains.

The confidence intervals for the secondary comparisons include zero, and the unadjusted p-values do not provide strong evidence of clear group differences. These comparisons are based on small posted outcome groups, and their estimates remain uncertain. The registry lists no reported analyses for these secondary outcomes; the posted comparisons are unadjusted recalculations from the summary statistics rather than documented sponsor-reported analyses. The registry record does not give an analysis plan specifying how these outcomes were to be tested or prioritized.

The secondary outcomes offer context for the primary quality-of-life result because they address concerns related to the workshop's transdiagnostic aim. They do not independently confirm or explain the primary result, and they do not demonstrate that changes in one domain account for any difference in another. The record does not report mediation analyses, correlations among outcomes, or an integrated model of the measures.

Multiple outcomes create a multiplicity concern: examining several comparisons increases the chance that at least one appears notable by chance, unless the analysis plan addresses that issue. Whether any adjustment or prespecified hierarchy was used is not reported in the registry record. For that reason, unadjusted secondary results carry less weight than results from a clearly prespecified, appropriately analyzed primary comparison. The overall pattern can be described, but it should not be treated as confirmatory evidence on its own.

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

• Military to Civilian Questionnaire (M2C-Q)
• PTSD Checklist-Civilian Version (PCL-C)
• Acceptance and Action Questionnaire-II (AAQ-II)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: each participant's quality-of-life scale score is represented by a number, and the registry reports group means. A mean gives a concise description of the center of the observed scores in a group. The registry also reports standard errors. A standard error describes the uncertainty in an estimated group mean; it is not the spread of individual participant scores. The record does not give the underlying standard deviations for this outcome.

What does the mean difference represent?

The posted comparison is the ACT on Life mean minus the treatment-as-usual mean. A positive estimate indicates that the reported ACT on Life mean is higher; a negative estimate would indicate that it is lower. For the primary outcome, the recalculated estimate is 0.91 units. This is a difference between group means, not a change from baseline: baseline outcome values and a change-score analysis are not reported in the registry record. The comparison is unadjusted, so it does not account for covariates or other factors through a reported model.

What does the confidence interval communicate?

A confidence interval gives a range of values that are compatible with the estimate under the statistical method used. It communicates uncertainty about the size and direction of a group difference. In repeated use of a method under its assumptions, intervals constructed this way would capture the true value at the stated confidence level with the method's stated long-run frequency. General statistical interpretation does not mean that a particular interval assigns a probability to the true value after the data have been observed. The primary interval, -3.957 to 5.777, includes zero, so the data are compatible with no difference as well as with differences in either direction.

How should the p-value be read?

The unadjusted p-value of 0.714 describes how unusual results at least as incompatible with a no-difference model would be under that model and the assumptions of the calculation. It is not the probability that the no-difference model is true, and it does not measure the size or practical importance of a difference. A large p-value does not establish that two groups are equivalent. The registry does not list a sponsor-reported analysis or a prespecified statistical method for the primary comparison, so the comparison should be understood as an unadjusted recalculation from posted summary statistics.

Why does the small analysis group matter?

Estimates from groups with limited numbers of participants can be imprecise, especially when individual outcomes vary. The confidence interval expresses some of that imprecision for the mean difference. The registry reports 19 participants in the ACT on Life primary outcome summary and 12 in the treatment-as-usual summary. It separately states that 27 were assigned to ACT on Life, of whom only 19 were eligible, had valid data, and began the workshop. The record does not describe the reasons for the difference or the methods, if any, used to address missing outcome data. This makes it important to distinguish the posted outcome population from everyone assigned.

What does an unadjusted comparison leave out?

An unadjusted comparison contrasts the group summaries without a reported model controlling for baseline scores or other participant characteristics. Random assignment is intended to support fair comparisons, but the registry record does not describe the randomization procedure or give baseline balance information. With the posted outcome groups, chance imbalances may remain possible. The record also does not state whether the reported comparison followed an intention-to-treat approach or a different analysis population. These are reasons to interpret the recalculation as a descriptive, limited comparison rather than as a fully documented analysis of the randomized trial.

General statistical concepts can help clarify what these values do not convey. A standard error is not an individual-level standard deviation, a confidence interval is not a guarantee that the effect lies within its endpoints, and a p-value is not a measure of clinical importance. The posted numbers support an estimate and an account of its uncertainty, but they do not resolve the limitations in analysis reporting or the population represented.

11. Confidence Intervals and Precision

The primary mean difference is 0.91 units, with a 95% confidence interval from -3.957 to 5.777. The interval crosses zero, so it includes no mean difference and values in either direction. Its breadth means that the estimate is not precise enough to distinguish a small difference from a substantially larger difference on the scale. The point estimate should not be interpreted without this range of uncertainty.

Precision depends in part on how much information the comparison contains. The posted outcome groups include 19 ACT on Life participants and 12 treatment-as-usual participants, and the registry reports standard errors of 1.94 and 1.55 for their means. The standard errors describe uncertainty around each mean, while the confidence interval describes uncertainty around the contrast. Neither tells how participants' individual scores are distributed unless additional information is reported.

A confidence interval that includes zero does not prove there is no difference, and it does not establish equivalence. The registry record does not report an equivalence margin or a noninferiority framework. Rather, the interval indicates that the observed data do not pin down the direction and magnitude of the mean difference with precision. The record's statement that 27 participants were assigned to ACT on Life but only 19 were eligible, had valid data, and began the workshop is also relevant to how representative the posted outcome summary may be. The reasons for that distinction and the handling of unavailable data are not reported in the registry record.

Thus, the primary comparison should be read as an uncertain estimate in the observed outcome groups. The confidence interval is more informative about that uncertainty than the point estimate alone, but it cannot compensate for missing details about the original analysis plan, missing-data methods, or analysis populations.

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 illustrations give participants per arm, not total events. They are not the trial's original sample-size justification: the original design assumptions are not reported in the registry record. The listed illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each row considers an effect to detect equal to a stated fraction of the observed effect. For example, planning for 75% of the observed effect means using a smaller target effect than planning for the full observed estimate.

The 80% power column describes the number of participants per arm that the illustration estimates would be needed to have an 80% chance of detecting the specified effect under the stated assumptions, if that effect were the true one. The 90% column uses a higher target chance of detection and therefore requires more participants per arm. For the primary outcome, the illustration for the full observed effect lists 1,049 participants per arm for 80% power and 1,404 participants per arm for 90% power. The smaller-effect rows require more participants: if the effect to detect is smaller, it is harder to distinguish from random variation without more information.

The curve represents the same planning relationship across effect assumptions; it is an illustration, not a forecast of what a future study will observe. These calculations are based on the observed effect, which can be imprecise in a small study and may not be a reliable estimate for planning. The values are planning illustrations, not observed power. Observed power is not a useful substitute for reading the effect estimate and its confidence interval after a study; the interval directly communicates the uncertainty in the posted comparison.

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 = 0.910; pooled standard deviation σ = 7.438.
2. n = 2 × (1.96 + 0.842)² × 7.438² / 0.910² = 1,048.7, rounded up to 1,049 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 <- 0.91                      # observed difference in means
sigma <- 7.43774437442632                     # 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(2844946)
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 = 1,049 (80% power), 1,404 (90% power)
 75% of observed effect: n per arm = 1,865 (80% power), 2,496 (90% power)
 50% of observed effect: n per arm = 4,195 (80% power), 5,616 (90% power)
power.t.test: 1049.6 
Simulated power at n = 1,049 per arm: 0.799 (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. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary outcome and three secondary outcomes, but it does not report how the statistical plan handled multiple outcomes or multiple comparisons. No multiplicity adjustment, hierarchy of endpoints, or prespecified decision rule is reported in the registry record. When several outcomes are examined, the chance of finding an apparently notable result by chance can increase. This general concern is relevant to interpreting the secondary comparisons, which are unadjusted and should be considered exploratory unless a prespecified plan indicates otherwise.

Missing-data methods are not reported in the registry record. For the primary outcome, the record says that 27 participants were assigned to ACT on Life, while only 19 were eligible, had valid data, and actually began the workshop. It does not explain why the other assigned participants are not represented in that outcome group, how eligibility and valid data were defined, or whether unavailable values were excluded, imputed, or handled in another way. The treatment-as-usual outcome summary includes 12 participants, but further information about the analysis population is not reported.

The registry record does not state whether analyses were based on everyone as randomized, on participants who began the workshop, or on another population. It also does not describe adherence, crossover, withdrawals, or how these might have been handled. Such details help determine whether the outcome comparison estimates the effect of being assigned to the workshop or the outcome among a selected group of participants with available data.

Although randomization is listed, the sequence-generation method, allocation concealment, and baseline comparisons are not reported in the registry record. A statistical analysis plan, covariate adjustments, and any interim analyses are also not reported. These omissions do not alter the arithmetic of the posted summaries, but they limit assessment of whether the analyses followed the intended protocol and whether missingness or selection could have influenced the estimates.

15. 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 lists serious adverse events for 19 participants at risk in the ACT on Life group and 12 at risk in the treatment-as-usual group. It records zero serious adverse events in each group. It also records zero other adverse events and zero deaths in both groups. No serious adverse-event terms are listed.

These figures describe events recorded in the registry for the groups and risk sets stated there. They do not establish that no events occurred outside the registry's reporting definitions or observation procedures, and they do not by themselves show that the groups had equivalent safety experience. The record does not provide further detail on event definitions, collection methods, follow-up completeness, or causal attribution. The numbers should therefore be read as the posted adverse-event counts, not as a complete characterization of all possible harms.

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

The primary result is an estimate of the difference in mean quality-of-life scores between the posted ACT on Life and treatment-as-usual groups over the stated follow-up timeframe. It does not directly describe what happened to each participant, whether individuals improved or worsened, or whether changes were sustained beyond study completion. Baseline scores and individual trajectories are not reported in the registry record.

The estimate and confidence interval do not establish that the workshop caused a difference. Randomization is reported, but details of the procedure, the analysis population, and missing-data handling are not reported. The outcome group for ACT on Life includes 19 participants, whereas the registry states that 27 were assigned to that group. The posted comparison therefore should not be assumed to represent every participant assigned to the intervention.

The result also does not establish equivalence between the groups. A confidence interval that includes zero can be consistent with no difference, but it can also include meaningful differences in either direction. The registry does not report a prespecified equivalence or noninferiority margin that would permit such a conclusion. Nor does the result demonstrate that the intervention works or does not work; it describes an uncertain estimate from the posted outcome summaries.

More broadly, one quality-of-life scale cannot capture every concern named in the study, and the secondary measures do not resolve the uncertainty in the primary estimate. The record does not report which workshop components participants used, the extent of participation, or whether any changes in particular skills explained the outcomes. The appropriate interpretation is limited to the outcome, time frame, and participants represented in the posted results. Broader claims about all veterans with these conditions or about effects in other settings are not established by this record.

17. Why This Trial Matters Statistically

This trial raises a useful statistical question about how to evaluate a brief, transdiagnostic intervention when participants may face several interacting concerns. A broad quality-of-life measure speaks to an outcome that is not confined to a single diagnosis, while the listed secondary measures address related but distinct areas. Considering the outcomes together can clarify the scope of the research question, but it also makes prespecification and careful interpretation of multiple comparisons important.

The example also shows why an effect estimate should be read with its uncertainty. A single mean difference can look straightforward, yet the confidence interval includes values on both sides of zero and is wide. Reporting the point estimate without the interval would conceal how limited the precision is. Conversely, relying only on a p-value would not describe the range of effects compatible with the data or establish equivalence.

The gap between the ACT on Life assignment count and the number included in its posted outcome summary highlights the importance of defining analysis populations and reporting missing-data handling. These details are essential for understanding whether an estimate concerns all randomized participants or a subset with available outcomes. The registry record does not report those methods, so the posted results are informative but limited.

Finally, planning illustrations based on an observed effect are not substitutes for an original sample-size rationale. They can show how target effect size and desired power relate to required participants, but they inherit uncertainty from the observed estimate. The record's lack of reported original design assumptions makes it especially important to distinguish these illustrations from the trial's own planning decisions.

18. 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 immediate limitation is the size and composition of the posted outcome groups: the primary summary includes 19 ACT on Life participants and 12 treatment-as-usual participants. The registry separately reports 27 assigned to ACT on Life, of whom only 19 were eligible, had valid data, and began the workshop. The reasons for this difference and how it affected the analysis are not reported in the registry record. This makes it difficult to assess possible selection or missing-data effects.

The registry does not describe the eligibility criteria in enough detail to determine how closely the analyzed participants represent the broader population of veterans with mild traumatic brain injury, distress-based psychopathology, and chronic pain. Specific recruitment settings and participant characteristics are not reported in the registry record. The intervention was a one-day workshop, but the extent of attendance, participation, or adherence beyond the statement that participants began it is not described.

The identity of the masked party, allocation concealment, randomization procedures, baseline outcome values, and details of usual care are not reported. The available comparison is an unadjusted recalculation from summary statistics, with no sponsor-reported analysis listed. The registry also does not report the original statistical plan, missing-data methods, analysis populations, or any multiplicity procedure. Those omissions constrain evaluation of potential bias and of whether the posted analyses match the intended plan.

Follow-up is described as through study completion, an average of 3 months following workshop attendance. Longer-term outcomes are not reported in the record. The primary scale is broad, and the listed secondary outcomes do not cover every possible consequence of the workshop. Together, these limitations mean that the findings are best interpreted as imprecise, outcome-specific summaries from the participants represented in the posted data.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: One-Day Life Skills Workshop for Veterans With TBI, Pain and Psychopathology — NCT02844946.
• Registry record last updated 2021-12-02; status last verified 2021-11.
• Results first posted 2019-08-28.
• 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.

22. Record Summary

The registry describes a completed, randomized, single-masked, parallel-group study of ACT on Life, a one-day Acceptance and Commitment Therapy-based workshop, compared with treatment as usual for veterans with mild traumatic brain injury, distress-based psychopathology, and chronic pain. The primary outcome was the WHO-QOL general Quality of Life scale, assessed through study completion, an average of 3 months following workshop attendance.

The primary mean difference was 0.91 units, with a 95% confidence interval from -3.957 to 5.777 and an unadjusted p-value of 0.714. The interval includes zero and indicates substantial uncertainty about the direction and size of the comparison. The primary outcome summaries include 19 ACT on Life participants and 12 treatment-as-usual participants; the registry states that 27 were assigned to ACT on Life, but only 19 were eligible, had valid data, and began the workshop.

Analyses, missing-data methods, analysis populations, multiplicity procedures, and the original sample-size rationale are not reported in the registry record. The sample-size illustrations are planning calculations based on the observed effect, not the trial's original design assumptions.