Biomechanical Validation of the Transfer Assessment Instrument (TAI): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Biomechanical Validation of the Transfer Assessment Instrument (TAI) (NCT01183546), a registered phase not stated study. The primary outcome is Transfer Performance (TAI Scores Part 1).

2. Clinical Question

The clinical aim is instrument development: to refine a way for therapists to evaluate how transfer techniques are performed. The central statistical question would be how the TAI scores are distributed and whether they change between the stated assessment times. Those results are not reported in the registry record, so the posted information cannot establish the size, direction, or precision of any score change. Nor does it establish whether the instrument distinguishes different levels of performance or produces consistent assessments. Those are possible measurement questions, not findings in this record.

3. Trial Design

The registry identifies the study as “Biomechanical Validation of the Transfer Assessment Instrument (TAI)” and lists the status as completed. The listed enrollment is 53. The start is recorded as 2012-08, and primary completion as 2014-12. The sponsor is the VA Office of Research and Development. These details situate the study but do not supply evidence about the primary outcome.

The stated purpose is to further develop and refine the TAI, a clinical tool for therapists to evaluate transfer techniques and performance. The listed study arm is wheelchair users with spinal cord injury. The record does not state an allocation method or describe a randomized design. It also does not give a like-for-like control arm, so the available description does not support interpreting the study as a controlled treatment comparison. A comparator is not reported in the registry record.

The primary outcome is Transfer Performance (TAI Scores Part 1), expressed in units on a scale and summarized as a mean with standard deviation. Its timeframe is baseline testing and follow-up testing (4 weeks). The listed secondary outcome is Shoulder Peak Resultant Moment. Although the registry lists two outcome measures, it records no analyses. It does not report outcome values, the number of participants contributing data at either assessment, or how the secondary measure was analyzed.

The registry record does not report a detailed protocol, a sample-size justification, or the statistical plan for the study itself. Planning assumptions associated with illustrative sample-size calculations are not evidence of the trial’s design or analysis plan. In particular, an equal-allocation assumption for a planning illustration does not establish that study participants were allocated equally between arms.

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 Transfer Performance (TAI Scores Part 1), measured over Baseline Testing and at Followup Testing (4 weeks).

The primary endpoint is Transfer Performance, measured with Part 1 of the Transfer Assessment Instrument. This part consists of 15 items. Each applicable skill receives “yes” and 1 point when performed correctly, “no” and 0 points when performed incorrectly, or “N/A” when the item does not apply. The summary score is calculated by summing item scores, multiplying by 10, and dividing by the number of applicable items. The resulting scale ranges from 0 to 10.

The measure is intended to capture transfer performance in a format that therapists can use to evaluate technique. A standardized score can make performance easier to describe than an unstructured narrative, while the N/A option allows items that do not apply to be excluded from the score denominator. These are general measurement considerations; the record does not report how the instrument performed in this study.

The registry specifies mean and standard deviation as the summary format and gives baseline testing and follow-up testing (4 weeks) as the timeframe. A mean describes the average score in the measured group; a standard deviation describes the spread of individual scores around that mean. Neither statistic is reported for this outcome. The registry record also does not report a score change, an uncertainty interval, or a test of change over time. The endpoint’s definition is available, but its observed results are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry is sparse. The primary endpoint is a continuous score, and the record specifies that it is summarized using a mean and standard deviation. It does not report the outcome values or analyses. The explanations below describe general statistical concepts and distinguish them from methods actually documented for this study.

What does a mean and standard deviation describe?

For a continuous outcome, a mean is the arithmetic average of observed values. It gives a summary of the group’s central score, but it does not show how scores are distributed or whether individuals have similar scores. The standard deviation is a measure of dispersion: it describes how much the observed scores tend to vary around their mean. A larger standard deviation generally corresponds to more spread in the measurements, while a smaller one corresponds to less spread. These are general explanations, not reported findings for this study.

The TAI Part 1 score is bounded, with a stated range from 0 to 10. A bounded score can have distributional features that differ from an unbounded continuous measure, particularly near the scale’s limits. The registry does not report the distribution of scores, whether values clustered near either limit, or whether the investigators evaluated assumptions for any statistical model. The record states the descriptive summary format, but not an inferential method.

How should repeated assessment be understood?

Baseline and follow-up testing (4 weeks) imply two planned measurement occasions for the primary endpoint. If the same participants contribute measurements at both times, their scores are paired: each follow-up value is connected to that participant’s baseline value. General methods for paired data account for this within-person relationship. Treating the observations as independent when they are paired can misstate uncertainty because measurements from the same person may be related. The registry record does not state whether the same participants were assessed at both times, how paired observations were handled, or whether a change analysis was conducted.

A within-person change estimate would describe the difference between each participant’s follow-up and baseline scores, summarized across participants. Its interpretation depends on the analysis population and the handling of missing observations. The record reports neither a change estimate nor a method for calculating one. It also does not report a confidence interval or a hypothesis test for change. Therefore, no particular paired-data method should be attributed to this study.

What do uncertainty and significance mean?

In general, a confidence interval communicates uncertainty around an estimate under the assumptions of the selected method. A narrow interval indicates greater statistical precision than a wide interval, but precision is not the same as clinical or measurement importance. A p-value, when used, describes how compatible the observed data are with a specified null model under the test’s assumptions; it is not the probability that the null hypothesis is true. Neither a p-value nor a confidence interval for the primary endpoint is reported in the registry record. There is no basis for describing the outcome as statistically significant or not significant.

The record contains planning assumptions for illustrative sample-size calculations: a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. Those are planning assumptions, not a report of the trial’s own design or analysis. The registry does not state that participants were equally allocated, and the listed study description is not a like-for-like control comparison. The record does not provide the calculated participant counts in the information available for this analysis, and no sample-size figure should be inferred from the assumptions. Planning illustrations are not observed power and do not show what the study found.

Why can over-dispersion matter?

As a general concept, over-dispersion occurs when observed variability exceeds what a statistical model assumes. When a model underestimates variability, standard errors can be too small and uncertainty intervals can be too narrow. Methods that account for extra variability may be appropriate in some settings. However, the registry identifies the primary measure as a continuous score and does not report a model, evidence of over-dispersion, or any adjustment for it. This concept should not be mistaken for a feature demonstrated in these data.

What can be said about the analysis plan?

The registry lists two outcome measures and zero analyses. It does not report the statistical methods used, the handling of repeated measures, covariate adjustment, an analysis population, missing-data procedures, or interim analyses. It also does not report a sample-size justification for the study. These omissions mean that readers cannot verify which analysis was planned or performed, or whether a reported estimate would follow a prespecified method. Since no outcome analyses are posted, recalculation from summary statistics is not possible. The proper interpretation is that the statistical results are not reported in the registry record, not that the results were null.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Baseline Transfer Testing", "Followup Transfer Testing")
n   <- c(11, 11)
m   <- c(6.31, 9.92)
sp  <- c(0.98, 0.25)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Baseline Transfer Testing  11  6.310  0.980  5.652  6.968
CARM  Followup Transfer Testing  11  9.920  0.250  9.752  10.088

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures: the primary Transfer Performance measure and the secondary Shoulder Peak Resultant Moment. It records zero analyses. No statistical analysis plan is reported, and the registry record does not explain whether the outcomes were tested, modeled, or summarized in a particular way. It also does not report any multiplicity adjustment or a hierarchy for interpreting multiple outcomes.

As a general principle, testing several outcomes can increase the chance of obtaining at least one apparently unusual result by chance if each is treated as a separate confirmatory test. Prespecified priorities and appropriate procedures can help readers understand how multiple comparisons were handled. No such procedures are reported. Because outcome analyses are absent, there are no posted p-values or estimates to interpret in light of multiplicity.

Missing-data information is also not reported in the registry record. The enrollment is 53, but the record does not give the number assessed at baseline or follow-up, the number with complete paired scores, reasons for missing observations, or the approach to missing data. These details matter because an analysis based only on participants with complete data may represent a different group from everyone enrolled. General methods can address missingness under specified assumptions, but no assumptions or method should be attributed to this study.

The registry does not define an analysis population, such as all enrolled participants or those with available measurements. It does not report interim analyses or the study’s sample-size justification. These absences limit assessment of prespecification and selective reporting, but they do not establish that analyses were or were not conducted outside the registry record.

12. 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 0% reporting threshold.

The serious-adverse-event listing is for wheelchair users with ASIA A or B spinal cord injury. It reports 53 participants at risk and 0 affected by a serious adverse event. The other adverse-event field also lists 53 at risk and 0 affected. The deaths entry is null, so deaths are not reported in the registry record; a null entry should not be read as a reported zero.

These are counts as recorded in the registry, not estimates of comparative risk. The record does not describe a control group or a randomized comparison, and it does not provide a detailed account of adverse-event definitions, collection methods, or event timing. The listed group title is more specific than the general arm description, and the record does not explain that relationship. The figures therefore describe the posted safety entries only.

A zero count in a registry entry means that no affected participants are recorded in that entry. It does not establish that an event is impossible or that a study can rule out uncommon events. The record’s enrollment and event counts also do not establish the number followed for the full study period. The safety information should be interpreted as limited registry reporting, not as a comprehensive assessment of risk.

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

The study’s stated purpose is to further develop and refine the Transfer Assessment Instrument, a tool intended for therapists evaluating transfer techniques and performance. The registry defines Part 1 of the instrument, explains its scoring, and identifies baseline testing and follow-up testing (4 weeks) as the primary outcome timeframe. This supports understanding what the investigators intended to measure.

It does not show the measured scores. No mean, standard deviation, change estimate, confidence interval, or primary-outcome analysis is reported in the registry record. The listed sample of 53 is an enrollment figure, not proof that 53 participants contributed complete primary-outcome data. As a result, the posted information cannot establish whether scores increased, decreased, or stayed similar, nor how precisely any change was estimated.

The record also does not establish that the TAI is reliable, valid, responsive to change, or useful in practice. Those are measurement properties that require relevant evidence and analysis; the study’s title and stated purpose are not evidence that any property was demonstrated. No finding about the secondary Shoulder Peak Resultant Moment outcome is reported either.

This is not a randomized treatment comparison in the information recorded: allocation is not stated, and the described arms are not a like-for-like control comparison. The record therefore does not support conclusions about the comparative effect of a treatment. Likewise, the absence of posted analyses should not be interpreted as evidence of no effect or no change. It means the registry record does not contain the results needed to make those judgments.

The narrow conclusion is that the registry documents a completed study with a defined performance measure, an intended assessment timeframe, and a stated instrument-development purpose. It does not provide the outcome evidence needed to assess what the study found.

14. Why This Trial Matters Statistically

This study is statistically interesting because its central task is measurement, not simply comparison of clinical interventions. A clinical instrument converts observed performance into a score. Interpreting that score requires attention to how items are defined, which items apply, how the total is formed, and how much scores vary across participants. The registry describes these scoring features for Part 1 of the TAI, including the N/A response and the bounded 0-to-10 scale.

Repeated measurement also raises design and analysis questions. When the same individuals are assessed at baseline and follow-up, the relationship between their measurements matters for estimating change and uncertainty. A registry record that specifies assessment times but does not report participant counts or an analysis leaves readers unable to assess this aspect of the evidence. The statistical method should match the measurement structure; the record does not state which method was used.

Instrument-development studies also illustrate the difference between a measure’s definition and evidence about its performance. A score can be carefully specified without the registry record establishing its reliability, validity, or responsiveness. Those properties require analyses and results, which are not reported. This distinction is important when considering whether a measurement tool is ready to support clinical or research decisions.

Finally, the record shows why enrollment, outcome definition, and statistical results are distinct pieces of information. Enrollment is 53, yet the number contributing outcome data is not reported; the endpoint is described, yet its values are absent; and planning assumptions do not disclose the study’s own design. Reading each element within its limits avoids treating a completed status or a detailed endpoint definition as a substitute for reported evidence.

15. 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 main limitation for statistical interpretation is that the registry record does not report primary or secondary outcome results. There are no means, standard deviations, change estimates, uncertainty intervals, or analysis results for Transfer Performance or Shoulder Peak Resultant Moment. Although the record lists two outcome measures, it records zero analyses. This prevents assessment of the magnitude, direction, and precision of any observed findings.

Enrollment is reported as 53, but outcome-specific sample sizes and follow-up completeness are not reported. The record does not state how many participants contributed baseline and follow-up scores, whether all paired observations were available, or how missing data were handled. That limits assessment of representativeness and potential bias from incomplete observations.

The design information is also limited. Allocation is not stated, and the available arm description is not a like-for-like control comparison. The registry does not describe the statistical methods, a detailed protocol, an analysis population, or a sample-size justification. The illustrative planning assumptions are not the trial’s own design details and cannot fill those gaps.

For safety, the record gives zero affected in the listed serious and other adverse-event fields, but deaths are not reported. It does not provide fuller context about event definitions, collection, or follow-up. The safety entries therefore cannot support a comprehensive risk assessment. These limitations concern what the registry record documents; they do not establish what analyses or additional information may exist elsewhere.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Biomechanical Validation of the Transfer Assessment Instrument (TAI) — NCT01183546.
• Registry record last updated 2016-03-10; status last verified 2016-02.
• Results first posted 2016-03-10.
• 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.

19. Record Summary

The registry record describes a completed study sponsored by the VA Office of Research and Development, with enrollment of 53 and a stated purpose of refining the Transfer Assessment Instrument. The study concerns wheelchair users with spinal cord injury. The primary outcome is Part 1 of the TAI, a score from 0 to 10 based on applicable transfer-skill items, assessed at baseline and follow-up (4 weeks). Shoulder Peak Resultant Moment is listed as a secondary outcome.

The record lists two outcome measures and zero analyses. It does not report outcome values, statistical results, participant counts by assessment, or a detailed statistical plan. Allocation is not stated, and the described arms are not a like-for-like control comparison. The serious-adverse-event listing reports 0 affected among 53 at risk; deaths are not reported in the registry record. The available information supports describing the study and its measurement, but not drawing conclusions about its outcome findings.