Robotic Walking Device to Improve Mobility in Parkinson's Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Robotic Walking Device to Improve Mobility in Parkinson's Disease (NCT03751371), a randomized na study. The primary outcome is Gait Velocity.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel-group trial of a robotic walking device for people with Parkinson’s disease. Its title concerns improving mobility, and its brief description frames the study around home and community walking. The planned enrollment was 45. The registry lists Ohio State University as sponsor and the study status as completed. It describes the study as Phase II, while the formal phase classification is NA.

Participants were assigned to walking training with the HWA device or to usual care. The registry’s arm descriptions identify these two groups, and the primary endpoint results are reported for 19 participants in the training group and 20 in usual care. The primary outcome was measured at 8 weeks. The endpoint notes missing gait-velocity data for one participant in the training group; the record does not give further detail about the missing measurement or how it was handled in any sponsor analysis.

The registry says masking was single, but does not identify which people involved in the trial were masked. It also does not report the sequence-generation method, allocation concealment procedures, the training schedule, the content of usual care, or other operational details. These details should not be inferred from the randomized design label alone.

The stated study aims address both the short-term impact of mechanical gait assistance on walking efficiency and ease, and the effect of longer-term HWA use on unassisted walking in the home and community. The posted primary outcome is gait velocity at 8 weeks. That measure is narrower than the full set of aims: the registry also lists the 6-Minute Walk Test, stride length, timing measures, and variability measures as secondary outcomes. The posted outcome list includes 13 secondary outcomes and 14 outcome measures overall.

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: Missing gait velocity data for one participant in the Training group

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 Gait Velocity, measured over 8 weeks.

The primary endpoint is gait velocity, defined in the registry as walking speed measured in meters per second. It is a continuous measure, and the posted group summaries use the mean and standard deviation. The reported timeframe is 8 weeks after the trial’s intervention period as recorded for the outcome; the registry does not provide more detail about the measurement visit or procedure.

Walking speed is used in this trial as a direct quantitative description of gait performance. In general, a continuous gait measure can capture gradations in performance rather than reducing each participant’s result to a yes-or-no category. A group mean gives a summary of the central value, while the standard deviation describes how spread out the individual measurements are around that mean. These are general statistical interpretations of the summary measures, not claims about the clinical importance of any particular value.

The endpoint result lists a mean gait velocity of 1.25 meters per second in each group. The corresponding standard deviations are 0.3 for walking training with the HWA device and 0.33 for usual care. The posted endpoint information records one participant in the training group as missing gait-velocity data, and the comparison is based on the reported group summaries. The registry record does not report a threshold for a clinically important change, a baseline-adjusted endpoint definition, or a detailed measurement protocol.

Gait velocity represents only one aspect of mobility. It does not by itself describe walking endurance, stride characteristics, gait timing, variability, or ability to walk in daily home and community settings. The other posted outcomes address some of these additional dimensions, but they do not change what the primary endpoint itself measures.

7. Results Posted in the Registry

• Walking Training With the HWA Device: mean 1.25 versus 1.25 on control; difference 0.00 (95% CI -0.20 to 0.20), standardized effect d = 0.00; z-test p = 1.000.

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.

6-Minute Walk Test

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Walking Training With the HWA Device: mean 416.93 versus 426.92 on control; difference -9.99 (95% CI -87.26 to 67.28), standardized effect d = -0.08; z-test p = 0.800.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Walking Training With the HWA Device and the control. The interval gives the range of effects that remain compatible with the data.

Stride Length

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Walking Training With the HWA Device: mean 128.96 versus 131.79 on control; difference -2.83 (95% CI -20.57 to 14.91), standardized effect d = -0.10; z-test p = 0.755.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Walking Training With the HWA Device and the control. The interval gives the range of effects that remain compatible with the data.

Double Support Time

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Walking Training With the HWA Device: mean 18.01 versus 16.77 on control; difference 1.24 (95% CI -1.91 to 4.39), standardized effect d = 0.25; z-test p = 0.441.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Walking Training With the HWA Device and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists 13 secondary outcomes that cover several dimensions of mobility, including walking endurance, stride length, timing during the gait cycle, and variability in timing. The posted secondary results therefore broaden the measured scope beyond the primary gait-velocity endpoint. They do not, however, turn the trial into a comprehensive evaluation of every aspect of home and community mobility described in the study aims.

Across the secondary outcomes with numerical summaries and comparisons, the reported estimates are mixed in direction. Their confidence intervals include zero, and the unadjusted p values do not provide strong evidence of a clear group difference in these posted comparisons. The secondary results should be interpreted in the context of their uncertainty rather than as a consistent directional pattern. Per-outcome estimates and their intervals are reported alongside the endpoint results; the broader point is that the secondary measures do not overturn the primary finding of equal displayed group means for gait velocity.

There is also a difference between the breadth of outcomes listed and the analyses reported. The registry lists 13 secondary outcomes, while the number of reported analyses is zero. Numerical outcome summaries and recalculated comparisons are available for some endpoints, but a sponsor analysis plan or full set of analysis details is not reported in the registry record. Therefore, the results do not show whether these outcomes were prespecified in a hierarchy or how the sponsor intended to interpret them together.

Multiplicity matters because examining many outcomes creates more opportunities for a nominally notable result to occur by chance, even when no underlying effect exists. This is a general statistical concern, not a claim about what happened in this trial. The displayed secondary p values are unadjusted, and the registry record does not report a multiplicity correction or a designated confirmatory secondary endpoint. That makes isolated secondary findings less persuasive than a result supported by a prespecified analysis strategy and interpreted with appropriate control of multiple testing.

The secondary measures can provide descriptive context, but they remain exploratory in the absence of reported analysis and multiplicity details. Their results also concern the stated 8-week timeframe. They should not be read as evidence about longer-term effects, unmeasured aspects of everyday mobility, or the clinical importance of differences for individual participants.

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

• 6-Minute Walk Test
• Stride Length
• Double Support Time
• Swing Time - Right Leg
• Swing Time - Left Leg
• Double Support Time Coefficient of Variation
• Swing Time Coefficient of Variation of Right Leg
• Swing Time Coefficient of Variation of Left Leg

9. Statistical Interpretation

10. Statistical Methods Explained

The registry identifies gait velocity as a continuous primary outcome and reports a mean and standard deviation for each group. A continuous outcome can take values across a measurement scale, such as meters per second. The mean summarizes the group’s central value, and the standard deviation describes the dispersion of individual measurements around that mean. These are descriptive summaries; by themselves they do not show how outcomes changed over time or establish why groups might differ.

How to read the group comparison

The posted comparison is a mean difference between walking training with the HWA device and usual care. For the primary outcome, the two reported means are both 1.25 meters per second, and the recalculated mean difference is 0.0. The sign convention in the comparison treats the device-training group as the first group and usual care as the reference. A positive difference would indicate a higher mean in the device-training group under that convention, while a negative difference would indicate a lower mean. This explanation of signs is general; the result itself is the posted estimate.

The recalculated comparison uses the posted summary statistics and is unadjusted. It is not a substitute for a more detailed sponsor analysis if such an analysis exists. The registry record does not report a primary analysis model, covariate adjustment, or a model-based sponsor estimate. No discrepancy is flagged between the posted group summaries and the recalculated comparison. The record does not report additional analyses for this outcome.

What a confidence interval conveys

In general, a confidence interval describes the range of effect estimates that are reasonably compatible with the observed data under a specified statistical procedure and its assumptions. It communicates uncertainty about the estimated difference, rather than only whether a test crossed a significance threshold. For the primary comparison, the interval includes zero and spans values on either side. That means the posted summaries are compatible with no difference as well as with differences in either direction under the recalculation. The registry does not report a clinical threshold that would separate negligible from important differences.

A confidence interval is not a guarantee that the true effect lies within its endpoints, and it does not incorporate uncertainties that the analysis does not model. For example, it cannot correct for unreported departures from the analysis assumptions, missing outcomes, or selective outcome reporting. Its interpretation depends on the design and statistical method behind it. The registry record does not state a sponsor analysis method for the primary result.

How to read a p value

In general, a p value quantifies how unusual a result at least as extreme as the observed result would be under a null hypothesis and the test’s assumptions. It is not the probability that a treatment has no effect, and it does not measure the probability that a finding is due to chance. Nor does it describe the effect’s clinical importance. The primary unadjusted p value is 1.0. It should be read alongside the estimate and its interval, rather than as a stand-alone verdict.

The comparison is a simple unadjusted recalculation from the posted means and standard deviations. It does not account for baseline values or any other covariates. Whether the sponsor conducted an adjusted analysis, and what its prespecified analysis plan might have been, are not reported in the registry record. The registry lists zero reported analyses.

Why spread and sample size matter

Standard deviations describe variability among individual measurements. Greater variability generally makes it harder to estimate a group difference precisely when the number of observations is held fixed. Likewise, fewer observations generally leave more uncertainty around an estimated mean difference. These are general statistical principles. For this primary outcome, the reported group sizes are 19 and 20, with standard deviations of 0.3 and 0.33 meters per second. The record notes missing gait-velocity data for one participant in the training group, but does not give a detailed account of missing-data handling.

Randomization is intended, in general, to make comparison groups similar on average with respect to measured and unmeasured characteristics. It does not guarantee exact balance in a particular trial, especially when the number of participants is limited. The registry record does not provide baseline outcome summaries or baseline balance information in the registry record for this result, so the primary comparison should not be described as a change-from-baseline estimate.

Planning illustrations are not trial power

Planning estimates associated with selected secondary outcomes are based on the observed effect, not on the trial’s own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation, and a normal approximation; the illustrations scale the observed effect to different stated fractions. These estimates are hypothetical planning illustrations, not observed power and not a retrospective measure of whether the completed trial was adequately powered.

Observed effects from a small trial can be unstable, so using them as planning inputs can yield planning values that are sensitive to the particular results. A planning exercise would ordinarily need a justified effect size and variance assumptions relevant to a future study. The registry record does not report the original sample-size justification, its assumed treatment effect, or the methods used to select a target enrollment. No planning illustration should be taken as evidence that the trial was designed to detect the effect ultimately observed.

General statistical interpretation also depends on multiplicity and missingness. Multiple outcomes or repeated analyses can increase the chance of at least one apparently notable result if no adjustment or hierarchy is specified. Missing outcomes can affect estimates if their absence is related to participant characteristics or outcomes. The registry lists many secondary outcomes and notes one missing primary gait-velocity observation in the training group, but the analysis plan, multiplicity approach, and missing-data method are not reported in the registry record.

11. Confidence Intervals and Precision

The primary mean difference is 0.0 meters per second, and its confidence interval includes zero, extending in both the positive and negative directions. This is the central precision point: the estimated difference is exactly zero at the displayed precision, but the interval indicates uncertainty around that estimate. The interval’s exact endpoints are not restated because they contain more than three decimal places.

In general, a confidence interval is more informative than the point estimate alone because it indicates which effect sizes remain compatible with the observed data under the statistical method. An interval that crosses zero does not establish that the true difference is zero. It also does not demonstrate equivalence unless the study defines a clinically acceptable range and evaluates the interval against that range. No equivalence margin is reported in the registry record.

The endpoint summaries include 19 participants in the device-training group and 20 in usual care. Their standard deviations are 0.3 and 0.33 meters per second. These figures give context for the variation in individual measurements, but they do not resolve uncertainty about the group difference. The record notes missing gait-velocity data for one participant in the training group and does not report a detailed missing-data analysis.

Precision is specific to this outcome and timeframe. The primary comparison concerns gait velocity at 8 weeks; it cannot be used as an interval estimate for endurance, stride length, gait timing, or longer-term community mobility. The registry does not report baseline-adjusted estimates or a sponsor analysis that could be compared with the unadjusted recalculation. Accordingly, the posted interval and estimate should be read as a summary-statistic comparison, not as a complete account of every possible analysis of the trial.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists 13 secondary outcomes in addition to the primary gait-velocity outcome. Considering several outcomes raises a general multiplicity issue: the more tests conducted, the greater the chance of observing at least one apparently unusual result under a collection of null effects. This does not mean that any particular secondary result is false; it means results need to be interpreted in light of how many comparisons were planned and how they were prioritized.

The registry record does not report a multiplicity adjustment, an outcome hierarchy, or a plan identifying which secondary outcomes were intended to be confirmatory. It lists zero reported analyses. The numerical secondary results include unadjusted comparisons, but the registry does not explain whether these reflect the complete set of analyses performed or how the sponsor accounted for multiple testing. As a result, isolated secondary p values should be treated cautiously and should not be given the same weight as a clearly prespecified primary analysis.

For the primary endpoint, the record notes missing gait-velocity data for one participant in the training group. The results list 19 observations in that group and 20 in usual care. The registry record does not report why the measurement was missing, whether the participant remained in any other analyses, how missingness was handled, or whether sensitivity analyses were performed. In general, missing data can affect results if the reason for missingness is related to the outcome or to participant characteristics. The fact that one observation is noted does not, by itself, establish the direction or size of any resulting bias.

The registry does not report the analysis population definition, such as whether all randomized participants were included according to their assigned groups, or whether analyses followed another rule. It also does not report a detailed statistical analysis plan, baseline adjustment, or an imputation procedure. These omissions limit the ability to assess whether the displayed summaries correspond to the intended primary analysis and how robust the results are to alternative handling of missing observations.

The primary comparison described in the statistical interpretation is an unadjusted recalculation from posted summary statistics. It should not be mistaken for a complete sponsor analysis. The registry record does not report the original sample-size justification or the planned treatment effect used in design calculations. These missing details matter for understanding the trial’s confirmatory intent, but they cannot be filled in by assumptions about common trial practice.

13. 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 reports zero serious adverse events among 23 participants at risk in the walking-training group and zero among 22 participants at risk in usual care. It also reports zero other adverse events in each group, using the same respective at-risk counts, and zero deaths in both groups. These are event counts as recorded for the trial.

Zero reported events does not establish that an intervention is free of risk. In general, event counts are interpreted in relation to the number of participants observed, the length and completeness of follow-up, and how events were defined and collected. The registry record does not provide further detail about adverse-event definitions, surveillance methods, event severity beyond the serious-versus-other categories, or the duration of safety follow-up.

The at-risk counts differ from the endpoint observation counts, so the two sets of numbers should not be treated as the same analysis population. The record does not explain the distinction or provide individual-level event information. These figures describe what was recorded in the registry, not a comparative safety estimate with an uncertainty interval. They are not sufficient to conclude that the groups had equivalent safety profiles or that events could not occur in other settings or populations.

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

The primary posted comparison answers a limited statistical question: the mean gait velocity at 8 weeks was 1.25 meters per second in each group, and the unadjusted recalculated difference was 0.0 meters per second. The p value was 1.0, and the confidence interval includes zero. This describes the observed group summaries and the uncertainty around their comparison.

It does not demonstrate that the approaches are equivalent. Equivalence requires a prespecified margin defining differences small enough to be considered practically similar, together with an analysis designed to test that question. The registry record does not report an equivalence margin or an equivalence analysis. Likewise, the result does not establish that the device-training approach has no effect; an estimate centered on zero can still be imprecise.

The result also does not answer every question raised by the study description. Gait velocity is one continuous measure at the stated 8-week timeframe. It does not, on its own, show whether participants walked more easily or safely, how far they could walk, how their mobility changed in their homes or communities, or whether any changes persisted. Other mobility outcomes are listed, but their presence does not expand the meaning of the primary endpoint.

The reported mean comparison is not a change-from-baseline estimate. Baseline gait-velocity summaries are not reported in the registry record, and no adjustment for baseline or other characteristics is described. The finding should not be generalized beyond the studied population, measurement, timeframe, and recorded trial procedures without evidence supporting that broader interpretation.

In general, statistical results are one part of evidence assessment. The size and precision of an estimate, the quality and completeness of the data, the analysis plan, and the relevance of the measured outcome all matter. Here, the registry record does not report several details needed to evaluate those aspects fully, including the sponsor’s detailed analysis plan, missing-data methods, and multiplicity strategy.

Accordingly, the posted data support a restrained description: the group means for the primary measure were equal at the displayed precision, and the recalculated comparison was uncertain enough to include differences in either direction. The result is not a recommendation and should not be read as a claim that the device does or does not improve mobility.

15. Why This Trial Matters Statistically

This trial is statistically instructive because its primary estimate is exactly zero at the reported precision, while the confidence interval still spans possible differences on both sides of zero. It illustrates why a point estimate and a test result do not tell the whole story. Readers need to consider the estimate’s uncertainty and the distinction between failing to identify a difference and demonstrating equivalence.

The reported primary groups are modest in size, and the endpoint record notes one missing gait-velocity measurement in the training group. With continuous outcomes, the precision of a mean comparison depends on both the number of observations and the variation in measurements. That general relationship helps explain why a centered estimate can coexist with meaningful uncertainty. It also underscores why sample-size assumptions and the intended effect size matter, although those original design details are not reported in the registry record.

The study’s stated aims reach beyond gait velocity, and the registry lists a broad set of secondary mobility outcomes. Such breadth can be useful for describing different aspects of movement, but it also makes a prespecified analysis hierarchy and multiplicity plan important. The registry record does not report these details. The secondary results therefore have to be read as a collection of uncertain comparisons rather than as a confirmed pattern.

The planning illustrations associated with secondary outcomes offer another statistical lesson: calculations based on observed effects are hypothetical planning exercises, not evidence of the completed trial’s power. In particular, they do not recover the assumptions that informed the original enrollment target. The record does not report that original justification.

More broadly, the record highlights how a concise result can leave important interpretive questions unanswered. Details about masking, missing data, analysis populations, and the intended statistical model help readers judge how results were generated. Where those details are not reported, clear boundaries around interpretation are part of sound statistical reporting.

16. 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 limitations specific to this trial affect interpretation. The primary outcome results are available as group means and standard deviations, with a recalculated unadjusted comparison, but the registry record does not report a detailed sponsor analysis or analysis plan. The posted comparison therefore does not show whether baseline values or other participant characteristics were incorporated in the planned analysis.

The record notes that gait-velocity data were missing for one participant in the training group. It does not explain the reason for the missing measurement, the method used to address it, or whether sensitivity analyses were conducted. The endpoint results list 19 participants in the device-training group and 20 in usual care, while the adverse-event record uses different at-risk counts. The registry does not explain these population differences.

Although the study is described as randomized and single-masked, the record does not identify who was masked or detail the randomization and allocation procedures. It also does not report the training dose, the usual-care content, or the gait measurement protocol. Those omissions make it harder to assess implementation and potential sources of measurement variation.

The trial’s stated interest includes home and community mobility and longer-term device use, but the primary posted endpoint is gait velocity at 8 weeks. The record does not establish that this measure captures all aspects of the broader aims or report longer-term primary results. There is no reported clinical-importance threshold for interpreting a gait-velocity difference.

Many secondary outcomes are listed, but a hierarchy and multiplicity strategy are not reported. Consequently, individual unadjusted secondary comparisons warrant caution. The registry record also does not report the original sample-size justification or the assumptions behind its enrollment target. These limitations do not invalidate the posted summaries, but they constrain what can be concluded from them.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: Robotic Walking Device to Improve Mobility in Parkinson's Disease — NCT03751371.
• Registry record last updated 2023-06-18; status last verified 2023-05.
• Results first posted 2023-06-18.
• 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.

20. Record Summary

The registry describes a completed randomized, single-masked, parallel-group study sponsored by Ohio State University, with planned enrollment of 45 and a focus on Parkinson’s disease. Participants received walking training with the Honda Walking Assist device or usual care. The primary outcome was mean gait velocity in meters per second at 8 weeks.

The primary group means were both 1.25 meters per second. The unadjusted recalculated mean difference was 0.0, with an unadjusted p value of 1.0; the confidence interval includes zero. The primary endpoint results list 19 participants in the training group and 20 in usual care, and the record notes one missing gait-velocity measurement in the training group.

The registry lists 13 secondary outcomes and reports zero analyses. Its adverse-event summaries record zero serious events, zero other events, and zero deaths in either group. Important details—including the sponsor’s analysis plan, missing-data handling, multiplicity strategy, and original sample-size justification—are not reported in the registry record.