Development and Evaluation of a Tonic Immobility Focused Psychoeducational Intervention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Development and Evaluation of a Tonic Immobility Focused Psychoeducational Intervention (NCT05113277), a randomized na study. The primary outcome is Posttraumatic Stress Disorder Symptoms.

2. Clinical Question

3. Trial Design

This was a randomized, parallel-group trial with single masking, conducted by Florida State University. Participants were assigned to Tonic Immobility Psychoeducation (TIP) or Health Education Training (HET). The registry classifies both interventions as behavioral. The trial status is completed; the recorded start date is 2021-09-27 and the primary completion date is 2022-03-31. The registry lists the phase as NA.

The trial was intended to evaluate a brief, web-based psychoeducational intervention among people who experienced tonic immobility in the context of trauma. The registry does not report the specific allocation procedure, the person or people masked, or details of the intervention sessions. The intervention descriptions state that participants in the experimental condition received TIP and participants in the control condition received HET; they do not describe further treatment procedures.

Enrollment was 51. The registry states that the final sample comprised 46 individuals: three participants did not complete the intervention, as determined during analysis after examining total time spent, and two were excluded from analyses because of significantly impairing drug use. Further details about the drug-use exclusion are not reported in the registry record. The reported primary arm sizes are 25 for TIP and 21 for HET.

The primary outcome was posttraumatic stress disorder symptoms, measured with the PCL-5 up to 1 month. The registry lists three outcome measures, but no statistical analyses and no secondary posted results. The trial's original sample-size justification, allocation details, masking procedures, and analysis plan are not reported in the registry record. These omissions mean that the posted record supports a description of the design and reported endpoint, but not a complete reconstruction of the planned statistical procedures.

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

Analysis population for the primary outcome, as defined in the registry: The final sample was comprised of 46 individuals. Of the 51 participants recruited, three participants failed to complete the intervention, as determined at the analysis phase after examining total time spent, and two participants were excluded from analyses due to significantly impairing drug use during the TI experience.

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 Posttraumatic Stress Disorder Symptoms, measured over up to 1 month.

The primary endpoint is posttraumatic stress disorder symptoms measured with the Posttraumatic Stress Disorder Checklist for DSM-5 (PCL-5). It is a continuous measure: responses across its 20 items are totaled to give a score ranging from 0 to 80. The registry states that lower values indicate better outcomes. The reported endpoint is the mean score up to 1 month, with a standard deviation describing variation among participants in each arm.

Using a validated symptom scale can make participants’ reported experiences measurable in a consistent way and permits comparison of average scores between randomized groups. A continuous score also retains more gradation than a simple category such as improved or not improved. The mean describes the group’s average score, while the standard deviation describes how dispersed individual scores are around that mean. Neither statistic shows the full distribution of scores.

The registry record gives a mean of 30.41 with a standard deviation of 18.23 for TIP, and a mean of 31.93 with a standard deviation of 18.33 for HET. The assessment timeframe is recorded as up to 1 month. The exact timing of measurement within that timeframe and the number of assessments are not reported in the registry record. The clinical importance threshold for interpreting a score difference is also not reported in the registry record, so the numerical contrast alone does not establish whether a difference would be meaningful to participants.

7. Results Posted in the Registry

• Health Education Training (HET): mean 31.93 versus 30.41 on control; difference 1.52 (95% CI -9.09 to 12.13), standardized effect d = 0.08; z-test p = 0.779.

8. Statistical Interpretation

9. Statistical Methods Explained

What is being compared? The outcome is continuous, meaning it is measured on a numerical scale rather than counted as an event or classified into categories. The primary endpoint is the PCL-5 mean score in each randomized arm. A comparison of means asks whether the groups’ average scores differ. Random assignment is intended to make groups comparable on average, but the registry record does not describe the allocation procedure or report baseline characteristics, so the degree of balance in this sample cannot be assessed from the listed information.

What does the mean difference represent? The reported estimate is 1.52 units, defined as the HET mean minus the TIP mean. The arm means are 31.93 for HET and 30.41 for TIP. A positive estimate therefore places the HET average above the TIP average; because lower PCL-5 scores indicate better outcomes, the point estimate is in the direction of a lower average score for TIP. A mean difference is expressed in the outcome’s units, here units on a scale. It is a group-level contrast, not a description of every participant’s response.

Why report standard deviations? The standard deviations are 18.23 for TIP and 18.33 for HET. A standard deviation summarizes how spread out individual scores are around the group mean. Similar standard deviations indicate similar observed spread in these groups, but they do not imply that the groups have the same score distribution or that their averages are the same. The registry record does not provide individual participant data or distribution plots, so the shape of the score distributions cannot be assessed from the summaries alone.

What does a confidence interval express? The 95% confidence interval for the mean difference runs from -9.088 to 12.13. In general, a confidence interval is a range of estimates compatible with the observed data under a statistical model and its assumptions. Its width conveys precision: a wider interval means greater uncertainty about the effect’s size. The interval includes zero, the value corresponding to no mean difference, and values in both directions. This means the data do not pin down whether the population mean is higher in HET or TIP. A confidence interval is not a probability statement that the true value lies inside this particular interval.

What does the p-value add? The unadjusted p-value is 0.779. In general, a p-value measures how unusual data at least as discrepant as those observed would be under a specified null hypothesis and model. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The high value, considered with the interval, indicates that the reported summaries do not provide precise evidence of a difference. The registry record lists no statistical analyses, so the test model and its assumptions are not documented there.

What does an unadjusted comparison mean? An unadjusted comparison contrasts the groups without accounting for additional covariates or other adjustments. In general, adjustment can be used to account for prespecified baseline variables or features of the design, but the registry record does not report whether an adjusted analysis was planned or performed. The comparison described by the posted means and standard deviations should not be interpreted as evidence that adjustment was unnecessary; the relevant analysis details are simply not reported.

Why can small samples produce uncertain estimates? In general, estimates from smaller samples tend to be less precise because each participant’s score has greater influence on the group summary. Here the analyzed arm sizes are 25 and 21, and the observed standard deviations are sizeable relative to the estimated difference. The confidence interval reflects the resulting uncertainty in the reported comparison. That uncertainty is distinct from whether the point estimate is large or small, and from whether a difference would be clinically important.

What does over-dispersion mean in general? Over-dispersion occurs when the observed variability is greater than a statistical model expects. It is particularly relevant to count or binary outcomes modeled with assumptions about variance. The primary outcome in this trial is a continuous score, and the registry record does not report an over-dispersion analysis. The recorded standard deviations describe observed variability but do not establish that over-dispersion is present.

What can be concluded from the record? The registry gives group summaries, an estimated mean difference, a confidence interval, and an unadjusted p-value, but lists no statistical analyses. The specification of the original test, any covariate adjustment, assumptions checks, handling of missing outcomes, and prespecified analysis procedures is not reported in the registry record. Thus, the statistical interpretation can describe the posted contrast and its imprecision, but cannot verify how a sponsor analysis was conducted or whether the reported comparison follows a prespecified plan.

10. Confidence Intervals and Precision

The estimated HET-minus-TIP difference is 1.52 PCL-5 units. Its 95% confidence interval extends from -9.088 to 12.13. The interval includes zero and spans both negative and positive differences. Accordingly, the point estimate alone gives a much narrower impression than the uncertainty interval: the data are compatible with a range of group differences in either direction.

In general, a confidence interval represents the range of effect estimates compatible with the data under the method’s assumptions. A narrower interval indicates greater precision; a wider interval leaves more uncertainty about the effect’s magnitude. The interval does not mean that there is a 95% probability that the true effect is between its endpoints. Its coverage interpretation applies to the procedure across repeated uses under the model assumptions.

The observed group standard deviations are 18.23 for TIP and 18.33 for HET, while the analyzed group sizes are 25 and 21. These summaries help describe the variability and sample size relevant to the uncertainty, but they do not establish why the interval has its particular width. The registry record does not report the analysis model or details of any adjustment.

The interval’s direction and breadth also limit claims about clinical relevance. The record does not identify a minimum clinically important difference or an equivalence margin. Without those criteria, the interval cannot establish that any compatible difference is important, unimportant, or clinically negligible. It supports a cautious reading: the posted result does not precisely determine the direction or size of the between-group difference.

11. 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, not total participants or total events. The sample-size illustration is based on the observed effect and assumes a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. For each effect scenario, the 80% power column describes the number of participants per arm in a planned study designed to have an 80% chance of detecting an effect of that stated size, if the assumptions hold. The 90% power column gives the corresponding planning target for a 90% chance.

For planning at 100% of the observed effect, the illustration gives 2,270 participants per arm for 80% power and 3,038 participants per arm for 90% power. For planning at 75% of the observed effect, it gives 4,035 participants per arm for 80% power and 5,401 participants per arm for 90% power. For planning at 50% of the observed effect, it gives 9,078 participants per arm for 80% power and 12,152 participants per arm for 90% power. Smaller effects require more participants to detect under the same planning assumptions.

These are planning illustrations calculated from the observed effect, not the trial’s original sample-size justification. The original design assumptions are not reported in the registry record. The figures are not observed power: they describe hypothetical future planning targets under the stated assumptions, not the probability that this completed trial detected an effect.

12. 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 = 1.520; pooled standard deviation σ = 18.276.
2. n = 2 × (1.96 + 0.842)² × 18.276² / 1.520² = 2,269.3, rounded up to 2,270 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 <- 1.52                      # observed difference in means
sigma <- 18.2755223778096                     # 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(5113277)
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 = 2,270 (80% power), 3,038 (90% power)
 75% of observed effect: n per arm = 4,035 (80% power), 5,401 (90% power)
 50% of observed effect: n per arm = 9,078 (80% power), 12,152 (90% power)
power.t.test: 2270.3 
Simulated power at n = 2,270 per arm: 0.803 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures, but the primary endpoint identified in the posted results is posttraumatic stress disorder symptoms measured with the PCL-5. No secondary results are posted, and the registry record lists no statistical analyses. It does not report a prespecified hierarchy among outcomes, the number of planned hypothesis tests, or any adjustment for multiple comparisons. Whether multiplicity was addressed in the trial’s analysis is therefore not reported in the registry record.

In general, testing multiple outcomes or multiple contrasts can increase the chance of finding an apparently unusual result by chance. A statistical plan may address that issue by specifying a primary outcome, an order for testing, or an adjustment method. The registry identifies a primary measure, but does not report whether the analysis plan included any of those procedures. No conclusions about multiplicity control can be drawn from the posted record.

The record says that three participants did not complete the intervention and two were excluded from analyses because of significantly impairing drug use. The analyzed primary endpoint groups contain 25 participants in TIP and 21 in HET, for a final sample of 46. The registry does not report the original randomized group sizes, outcome completeness by arm, reasons for any missing endpoint measurements beyond the stated reasons, or the procedure used to handle missing data. It also does not report whether the analysis followed intention-to-treat, per-protocol, or another population definition.

In general, missing-data methods matter because results can depend on why information is missing and how the analysis treats it. Excluding participants or imputing scores may affect estimates and uncertainty differently. With no reported methods or sensitivity analyses, the impact of noncompletion and exclusions on the primary comparison cannot be assessed.

Interim analyses, stopping rules, and the trial’s original statistical analysis plan are not reported in the registry record. The absence of those details is not evidence that particular procedures were or were not used; it limits what can be verified from the posted information.

14. 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 26 participants at risk in the TIP group and 25 participants at risk in the HET group. It records zero participants with serious adverse events in each group. It also records zero participants with other adverse events in each group and zero deaths in both groups.

These figures describe the events recorded in the registry for the stated groups at risk. They do not establish that no adverse events occurred outside the recorded categories, observation period, or reporting procedures. The registry does not report further detail about safety monitoring, the duration of adverse-event follow-up, or how events were collected and classified.

The numbers at risk for these safety summaries differ from the primary outcome arm sizes of 25 for TIP and 21 for HET. The registry record does not explain the difference. Safety figures should therefore be read in their own recorded populations and not assumed to correspond exactly to the analyzed symptom-score groups. The recorded zero counts are descriptive; they do not by themselves demonstrate the absence of risk or permit a precise estimate of uncommon events.

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

The posted result is an estimated mean difference of 1.52 PCL-5 units, with HET minus TIP as the direction of comparison. The average score was 30.41 in TIP and 31.93 in HET. Since lower values indicate better outcomes, the point estimate is directionally consistent with a lower average symptom score in TIP. However, the 95% confidence interval, from -9.088 to 12.13, includes no difference and estimates in either direction. The unadjusted p-value is 0.779.

These statistics do not establish that TIP is effective, ineffective, superior, equivalent, or harmful. A non-significant p-value does not prove there is no difference, and a point estimate in one direction does not prove a treatment effect. The interval shows that substantial uncertainty remains about the direction and magnitude of the difference. A clinical interpretation would also require a threshold for meaningful change, which is not reported in the registry record.

The result applies to the reported primary endpoint and analyzed sample. The registry describes participants who experienced tonic immobility in a traumatic context and reports 46 individuals in the final sample. Generalization beyond this population, intervention format, comparator, and assessment timeframe requires evidence not contained in the posted record. The outcome was assessed up to 1 month; longer-term results are not reported in the registry record.

The record does not report the analysis plan, missing-data methods, baseline characteristics, or statistical analyses. These omissions restrict evaluation of the assumptions behind the comparison and the potential effects of exclusions. The registry lists three outcome measures but posts no secondary results. Consequently, the primary estimate can be described, but it cannot be placed alongside a fuller set of outcomes or checked against a detailed prespecified statistical analysis.

The most defensible statistical reading is that the reported group means are close in their observed values, while the interval remains broad and includes materially different possibilities. This is an uncertain estimate, not a conclusive demonstration of similarity or difference.

16. Why This Trial Matters Statistically

This trial raises statistical questions common to behavioral intervention research: how to estimate a difference between randomized groups, how much uncertainty surrounds that estimate, and how to interpret a non-significant result when the confidence interval is broad. The primary comparison gives a concrete example of why the point estimate, interval, and p-value should be considered together rather than treating any one statistic as a complete answer.

The continuous PCL-5 endpoint retains variation in symptom scores and allows comparison of group means. At the same time, the result is shaped by the analyzed sample and the variability in scores. The registry reports a final sample of 46 and standard deviations of 18.23 and 18.33, alongside a wide confidence interval. That combination makes precision an important part of interpretation: the observed estimate does not narrowly determine the effect’s size or direction.

The sample-size illustration also shows how planning depends on the effect a future study aims to detect. Its targets rise as the assumed effect becomes smaller, under the stated planning assumptions. Because those figures are based on the observed effect rather than the original design, they should be understood as planning scenarios, not evidence about the completed trial’s power.

Finally, the registry’s limited reporting of analysis methods illustrates why a numerical result is not the same as a complete statistical account. Details about multiplicity, missing data, analysis populations, and the planned model matter for assessing how robustly the posted contrast addresses the research question. The result is useful for describing the recorded comparison, while the unreported methods constrain stronger interpretation.

17. 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 primary outcome analysis includes 46 individuals, with 25 in TIP and 21 in HET. The record states that three participants did not complete the intervention and two were excluded from analyses because of significantly impairing drug use. Further details about that exclusion are not reported in the registry record. The randomized group sizes and the effects of these exclusions on the result are also not reported, limiting assessment of selection and missing-data concerns.

The confidence interval for the primary mean difference is broad and includes values favoring either group. The registry does not report a clinically important difference threshold, so the practical importance of estimates within the interval cannot be determined from the record. It also does not report longer-term primary outcome results; the recorded timeframe is up to 1 month.

The registry lists three outcome measures but posts no secondary results and no statistical analyses. The analysis model, covariate adjustment, multiplicity procedures, missing-data methods, and analysis population are not reported in the registry record. Baseline characteristics, detailed allocation procedures, and the identity of those masked are also not reported. These gaps prevent a full appraisal of balance, analysis assumptions, and the potential influence of missing information.

The planned intervention is described as brief and web-based, but the registry record does not provide detailed content, delivery, or adherence information beyond noting that three participants failed to complete the intervention after total time spent was examined. The comparator’s content is similarly not described in detail. Consequently, the extent to which the two conditions differed in their non-specific features cannot be evaluated from the record.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Development and Evaluation of a Tonic Immobility Focused Psychoeducational Intervention — NCT05113277.
• Registry record last updated 2024-08-23; status last verified 2024-04.
• Results first posted 2024-08-23.
• 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.

21. Record Summary

NCT05113277 is a completed randomized, parallel-group trial sponsored by Florida State University. It compared Tonic Immobility Psychoeducation (TIP) with Health Education Training (HET) among people who experienced tonic immobility in the context of trauma. The registry records single masking and lists the phase as NA.

The primary outcome was PCL-5 posttraumatic stress symptom score up to 1 month. The reported means were 30.41 for TIP and 31.93 for HET. The HET-minus-TIP mean difference was 1.52, with a 95% confidence interval from -9.088 to 12.13 and an unadjusted p-value of 0.779. The final analysis sample was 46.

The record lists three outcome measures but no statistical analyses and no secondary posted results. It records zero serious adverse events, other adverse events, and deaths in both groups. Further details on analysis methods, missing data, and the original sample-size justification are not reported in the registry record.