The Effect of Power Posing on Timed Up and Go Test Score: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effect of Power Posing on Timed Up and Go Test Score (NCT03032393), a randomized na study. The primary outcome is Timed up and go Test.

2. Clinical Question

In plain terms, the research question is whether the average reported change in the time needed to complete the test differed between participants assigned to the high-power posture and those assigned to the low-power posture. The outcome description says the test was performed before and after the posture intervention at the same session. It does not specify the arithmetic convention used to calculate change, so the direction of a positive or negative change should not be given a more specific interpretation than the registry supports.

The registry record identifies the participants as healthy volunteers rather than describing a clinical patient group. It does not report participant-level characteristics or explain whether the results were intended to apply to any particular patient population. The study question is therefore about the measured test-time changes in these two groups, not about a broader clinical outcome.

3. Trial Design

The study is listed as randomized, with a parallel-group model and no masking. Its status is completed. The registry record lists enrollment of 30 participants and the primary completion date as 2017-12-31; the study start date is 2017-02-03. The sponsor is Youngstown State University. The phase is listed as NA.

Participants were assigned to one of two posture groups. The Dominant group was instructed to use the high-power posture, standing with hands on hips, elbows pointing out, and feet approximately one foot apart for 20 seconds. The Submissive group was instructed to use the low-power posture, wrapping hands and arms around the torso with feet together for 20 seconds. Each group has 15 participants in the posted outcome results.

The primary outcome is a continuous measure: the mean change in Timed Up and Go test time, measured in seconds. The test was assessed before and after the postural intention at the same session. The stated timeframe is up to 3 minutes during each test. The post-intervention measurement was taken immediately after the intervention; the pre-intervention measurement was at baseline.

Randomization details, including how the sequence was generated and whether allocation was concealed, are not reported in the registry record. The record identifies no masking, but does not describe which study personnel, if any, knew group assignments. Recruitment procedures, detailed eligibility rules, participant flow, and the rationale for the planned enrollment are also not reported. The registry record lists no analysis records, although it does post group-level outcome summaries and a summary-statistic comparison.

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 Timed up and go Test, measured over Up to 3 minutes during each Timed up and go Test. Twice (pre and post the postural intention) at the same session (day)..

The primary endpoint is the change in time to complete the Timed Up and Go test, reported as a mean in seconds with standard deviation. The test begins with the participant seated in a standard arm chair. The participant stands, walks to a line 3 meters or 10 feet away, turns, walks back, and sits down again. The recorded time is the duration required to complete that sequence.

The test combines several observable tasks: rising from a chair, walking, turning, returning, and sitting. As a general statistical point, a continuous time measure preserves the magnitude of each participant’s result rather than reducing it to categories. Reporting a group mean describes the average result, while a standard deviation describes the spread of individual results around that average.

The registry specifies that the outcome is a change between the pre- and post-intervention tests. This allows the reported group summaries to describe how test time changed over the session, and the comparison to focus on the difference between those reported changes. The registry does not specify the subtraction order used to form the change score. Therefore, the signs of the group estimates can be reported as posted, but a positive or negative sign should not be translated into faster or slower performance without that convention.

The test is used as a timed functional task, not as a direct measure of every aspect of mobility or health. The registry record does not report additional primary outcomes, a clinically meaningful threshold, or a rationale for selecting this endpoint.

7. Results Posted in the Registry

• Submissive: mean 0.20 versus -0.17 on control; difference 0.37 (95% CI -0.02 to 0.76), standardized effect d = 0.67; z-test p = 0.066.

8. Statistical Interpretation

9. Statistical Methods Explained

The posted primary outcome is continuous: mean change in Timed Up and Go test time, in seconds. The group summaries report a mean and standard deviation for each posture group. A mean gives the arithmetic average of the observations in a group. A standard deviation describes how dispersed the observations are around that mean. In general, a larger standard deviation indicates more variability among individual measurements, while a smaller one indicates that observations are more closely clustered around the group mean.

What does the group difference represent?

The comparison reports a mean difference of 0.37 seconds, with the Submissive group contrasted against the Dominant group. The group means are 0.2 seconds for Submissive and -0.17 seconds for Dominant. The difference is a comparison of those reported mean changes; it is not a separate measurement taken from participants. The registry record does not define whether each change was calculated as post-intervention minus baseline or baseline minus post-intervention. Without that detail, the sign of the change cannot safely be translated into a directional statement about test time.

The record gives the primary outcome timeframe as up to 3 minutes during each test and says measurements occurred at baseline and immediately after the posture intervention during the same session. The reported endpoint is the change between those assessments. The record does not provide individual observations, distributions, or a description of how missing pre- or post-test measurements were handled.

How should the confidence interval be read?

In general, a confidence interval describes uncertainty around an estimated quantity. For this comparison, the 95% interval ranges from -0.024 to 0.764 seconds when rounded to three decimal places. The interval includes zero, the value corresponding to no difference between the group mean changes. It also spans estimates on both sides of zero. This means the posted estimate is compatible with a range of possible differences, including little or no separation between groups. The interval is not a range containing every participant's change; it concerns the estimated difference in group means.

The record does not state the method used for the sponsor's statistical analysis, and it lists no analysis records. The comparison is therefore best described as an unadjusted summary-statistic comparison of the posted group data. No covariate-adjusted estimate or model specification is reported. In general, adjustment can account for specified variables, but no such analysis should be assumed when the record does not describe one.

What does the p-value add?

The unadjusted p-value is 0.066. In general, a p-value measures how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of the estimated difference. The registry does not report the trial's prespecified significance threshold or full testing procedure. The separate sample-size planning assumptions use a two-sided significance level of 0.05, but that planning value should not automatically be treated as the trial's original analysis rule.

For context, the p-value is above 0.05, while the confidence interval includes zero. These are consistent features of the reported unadjusted comparison. They do not establish that the groups are identical; rather, the estimate and its uncertainty do not isolate a nonzero difference at that threshold. The magnitude and precision of the estimate remain important even when a p-value is considered.

Why can variation matter?

In general, over-dispersion means that variability is greater than a model expects. That can make standard errors and confidence intervals too small if the model fails to account for the extra variation. The registry reports standard deviations of 0.65 and 0.43 seconds in the two groups, but it does not report an over-dispersion assessment or a model that assumes a particular variance structure. No claim about over-dispersion can be made from the registry record alone.

The study has 15 participants in each group. Small group sizes can make estimates sensitive to the observations included, and they often leave substantial uncertainty about the group difference. This is a general consideration, not evidence that any particular observation affected this estimate. The record does not provide participant-level data that would allow such an assessment.

What information is missing from the statistical plan?

The registry record does not report the original sample-size justification, the planned primary analysis method, handling of missing data, an analysis population definition, or any interim analyses. It does not report multiplicity procedures or a prespecified hierarchy of tests. These details matter because they define which outcomes and comparisons were planned, how uncertainty was quantified, and how incomplete observations or multiple tests were handled. Their absence means those design choices cannot be reconstructed from the posted results. The observed summaries can still be described, but they should not be presented as evidence that an unreported plan was followed.

10. Confidence Intervals and Precision

The estimated mean difference between the reported group changes is 0.37 seconds, with a 95% confidence interval from -0.024 to 0.764 seconds after rounding the bounds to three decimal places. The interval is the central measure of precision for this comparison: it shows that the estimate is uncertain and compatible with values on either side of zero. It is not a prediction interval for individual participants and does not describe the spread of all test times.

Because the interval includes zero, the posted results do not narrowly distinguish a nonzero difference from no difference. The upper and lower ends are meaningfully separated, so the estimate permits a range of possible effects rather than supporting a precise single value. The group standard deviations, 0.65 seconds for Dominant and 0.43 seconds for Submissive, describe variation within each group; they are not confidence limits for the group difference.

In general, a confidence interval reflects both the observed estimate and its sampling uncertainty under the method used to calculate it. It does not account automatically for every source of uncertainty, such as an unclear change-score convention, unreported missing-data procedures, or limits on how well the enrolled volunteers represent another population. Those issues remain relevant when interpreting the interval.

The registry record does not report the confidence-interval method or the trial's full statistical analysis plan. The posted comparison is unadjusted, and the interval should be understood as belonging to that comparison rather than to an adjusted model. The interval's inclusion of zero does not prove equivalence, and the record reports no equivalence margin or non-inferiority design.

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 event counts. They are illustrations based on the observed effect, not the trial's own original design assumptions. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect.

For the full observed effect, the illustration lists 35 participants per arm for 80% power and 47 participants per arm for 90% power. For planning at 75% of the observed effect, it lists 62 participants per arm for 80% power and 83 participants per arm for 90% power. For planning at 50% of the observed effect, it lists 140 participants per arm for 80% power and 187 participants per arm for 90% power.

In plain language, power is the chance that a study would detect an effect of a specified size under the planning assumptions, if that effect were present. The 80% power column gives the estimated number in each arm for that target; the 90% power column gives the larger per-arm target for a higher chance of detecting the same specified effect. Smaller effects require more participants, as the listed planning scenarios illustrate.

These figures are not observed power. They do not describe the probability that the completed study's findings are correct, and they are not the number of participants actually enrolled. The registry record does not report the original sample-size justification or its planning assumptions, so the illustrations should not be treated as the trial's intended design calculation.

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 = 0.370; pooled standard deviation σ = 0.551.
2. n = 2 × (1.96 + 0.842)² × 0.551² / 0.370² = 34.8, rounded up to 35 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 <- 0.37                      # observed difference in means
sigma <- 0.551089829338194                     # 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(3032393)
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 = 35 (80% power), 47 (90% power)
 75% of observed effect: n per arm = 62 (80% power), 83 (90% power)
 50% of observed effect: n per arm = 140 (80% power), 187 (90% power)
power.t.test: 35.8 
Simulated power at n = 35 per arm: 0.791 (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 record lists one primary outcome measure and no posted secondary outcomes. It does not report a multiplicity adjustment, a hierarchy of hypotheses, or a prespecified plan for handling multiple tests. With one primary outcome listed, the record gives no basis for inferring what testing procedures may have been intended beyond that outcome.

Multiplicity refers, in general, to the increased chance of at least one false-positive result when multiple hypotheses are tested. Statistical approaches can account for multiple comparisons, but no approach should be attributed to this study because the registry record does not report one. The unadjusted p-value of 0.066 is a result for the posted summary comparison; no adjusted p-value is reported.

Missing-data procedures are also not reported. The record does not say whether all randomized participants completed both assessments, how incomplete measurements were handled, or whether any participants were excluded from the outcome summaries. The posted group results list 15 participants in each arm, matching the enrollment count, but that alone does not describe the participant flow or establish how missing data were assessed.

The registry record lists no analysis records and does not define an analysis population, such as all randomized participants or only participants with complete outcome data. It also does not report whether the analysis followed assigned groups or used another population definition. These omissions do not change the arithmetic of the posted group summaries, but they limit assessment of how those summaries were selected and whether the analysis followed a prespecified plan.

In general, a clear analysis plan helps readers distinguish confirmatory analyses from exploratory comparisons and understand how missing observations and multiple tests affect inference. Those details are not reported in the registry record, so interpretation should stay with the posted outcome summaries and their unadjusted comparison.

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 15 participants at risk in each group. It reports zero serious adverse events in the Dominant group and zero in the Submissive group. The record also lists 15 participants at risk in each group for other adverse events and reports zero in both groups. No deaths are listed, and no serious-event terms are posted.

These figures describe what is entered in the registry for this study. They should not be read as proof that the posture instructions are free of risk or that adverse events could not occur. The record does not report detailed safety monitoring procedures, how events were defined or collected, or the duration of follow-up beyond the described testing session. It also does not provide event-level details for any category.

In general, absence of reported events in a small group is different from evidence that an event is impossible. The safety figures are limited to the participants and reporting captured in the registry record, and they do not establish safety in other populations or settings.

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

The posted results estimate a difference of 0.37 seconds between the mean changes in Timed Up and Go test time for the Submissive and Dominant groups. The estimated difference is accompanied by a 95% confidence interval from -0.024 to 0.764 seconds when rounded to three decimal places, and an unadjusted p-value of 0.066. The interval includes zero, indicating that the posted data do not rule out no difference between the group mean changes.

The results do not establish that the groups have identical outcomes. An estimate near zero and an interval spanning zero can reflect uncertainty, especially when each group has 15 participants. Conversely, the estimated difference does not by itself demonstrate a meaningful or important effect. The registry record does not report a threshold for clinical importance, and it does not state the subtraction convention for the change score. The signs of the group means therefore should not be translated into a claim about which group became faster or slower.

The study concerns healthy volunteers and a brief posture instruction followed by a timed task at the same session. The record does not establish whether findings apply to patients, longer periods, different tasks, or other settings. The registry also does not report detailed participant characteristics, the original statistical plan, missing-data procedures, or randomization methods.

These findings are best understood as a small randomized study's posted group summaries and unadjusted comparison. They do not, by themselves, settle a broader question about posture or establish a clinical consequence. The confidence interval and limitations in the record are as important to interpretation as the single estimated difference or p-value.

16. Why This Trial Matters Statistically

This trial is a useful example of why a statistical result should be read through its estimate and uncertainty, not through a p-value alone. The reported difference in mean change is 0.37 seconds, while its confidence interval crosses zero and spans both negative and positive values. Together, those features show that the data leave uncertainty about the direction and size of the group difference.

The design also illustrates the importance of clearly defining a change score. The registry says the outcome is a change from baseline to immediately after the posture intervention, but does not report the subtraction order. That missing detail affects how readers can describe the sign of the change. A result can be numerically clear while its directional interpretation remains limited by how the outcome was defined.

The study has 15 participants per group and reports standard deviations for the continuous endpoint. This makes it possible to describe both group averages and within-group variation, while the confidence interval communicates uncertainty in the between-group estimate. The planning illustrations further show, in general, how a smaller effect target requires more participants under stated assumptions. They are distinct from the actual enrollment and from the trial's unreported original design calculation.

Finally, the registry record makes visible the difference between posted results and a fully described statistical plan. It reports group summaries and an unadjusted comparison, but not the analysis population, missing-data rules, multiplicity approach, or analysis method. Recognizing those gaps is part of sound statistical interpretation: it helps separate what the numbers support from what cannot be inferred.

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.

Several trial-specific limitations are apparent from the registry record. The study enrolled 30 healthy volunteers, with 15 participants in each group, and the record does not report detailed participant characteristics or recruitment procedures. The findings therefore describe the posted results in these groups; their relevance to other populations is not established by the record.

The outcome is a pre-to-post change measured during the same session, with the post-test immediately after the posture instruction. The registry does not specify the arithmetic convention for calculating change. This prevents a fully grounded interpretation of whether a positive or negative change corresponds to a longer or shorter test time. The time frame is described as up to 3 minutes during each test, but no other follow-up outcome is posted.

The record identifies the study as randomized and unmasked, but does not report sequence generation, allocation concealment, or which personnel knew assignments. It also does not report participant flow, missing-data handling, or the analysis population. The group summaries list 15 participants per arm, but do not supply the additional details needed to assess exclusions or incomplete measurements.

The registry lists no analysis records and does not report the original sample-size justification, planned analysis method, interim analyses, or multiplicity procedures. The posted comparison is unadjusted, and no adjusted or secondary outcome results are reported. The confidence interval includes zero, and the estimate is based on a small number of participants. Together, these features counsel against treating the estimate as precise or broadly generalizable.

Finally, the safety record lists no adverse events, but does not describe event-collection procedures or longer-term monitoring. The available entry is limited to the safety reporting recorded for this study.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: The Effect of Power Posing on Timed Up and Go Test Score — NCT03032393.
• Registry record last updated 2020-08-10; status last verified 2020-08.
• Results first posted 2020-08-10.
• 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

The registry record describes a completed, randomized, parallel-group study with no masking and enrollment of 30 healthy volunteers. The two groups were assigned to brief high-power and low-power posture instructions, described as Dominant and Submissive. The primary outcome was mean change in Timed Up and Go test time, measured in seconds before and immediately after the posture intervention.

The posted group mean changes are -0.17 seconds for Dominant and 0.2 seconds for Submissive. The unadjusted mean difference, comparing Submissive with Dominant, is 0.37 seconds, with a 95% confidence interval from -0.024 to 0.764 seconds when rounded to three decimal places and an unadjusted p-value of 0.066. The interval includes zero.

The registry lists no serious or other adverse events in either group. It does not report the original sample-size justification, detailed analysis plan, missing-data procedures, or analysis population. The results should therefore be read as posted group summaries with an unadjusted comparison and the accompanying uncertainty.