This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Use of "Smart Wheelchairs" to Provide Independent Mobility to Visual and Mobility Impairments (NCT00333762), a na na study. The primary outcome is Time to Complete Trial Wheelchair Course.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00333762 |
| Phase | NA |
| Condition | Blindness, Spinal Cord Injury |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 4 |
| Arms in the primary outcome | n/a |
| Lead sponsor | VA Office of Research and Development |
| Results posted | Yes |
2. Clinical Question
Population
The project concerned people with visual impairment and people with both visual and mobility impairment. The brief summary distinguishes group trials involving people with visual impairment but no mobility impairment from single-case studio work involving people with visual and mobility impairment. Blindness and spinal cord injury are listed as conditions. The registry record gives an enrollment of 4, but it does not report the participant characteristics or how participants were distributed across those project activities.
Intervention
The listed devices are the Smart Power Assistance Module (SPAM) for manual wheelchairs and the Smart Wheelchair Component System (SWCS) for power wheelchairs. The arm description names SPAM and SWCS together. The project goal was to evaluate the systems in realistic indoor environments while target users performed realistic tasks.
Comparator
The registry record describes a single-group model and lists one arm, named “SWCS and SPAM.” Allocation is recorded as NA, and there is no like-for-like control arm in the record. The project description's reference to different trial activities does not establish a controlled comparison between devices or between a device and usual wheelchair use.
Primary question
The registered primary outcome was time to complete an indoor wheelchair course. The course included a straight path, 90 degree turns, and randomly placed obstacles. The record says time was recorded to assess whether SPAM or SWCS could detect objects, but it also states that no data were collected. Thus, the registry identifies the intended measure and setting, but does not report a measured completion time or a result about object detection.
The question is therefore best understood as an evaluation goal, not as a reported estimate of device performance. The record does not establish whether completion times were compared across users, across devices, or against a baseline. It also does not say how the two device systems related to the activities described in the summary. Without collected outcome data or a stated comparison, the record cannot answer how much time users took or whether one system differed from another.
3. Trial Design
This is a completed study record for NCT00333762, sponsored by the VA Office of Research and Development. The registry lists a single-group model, one arm named “SWCS and SPAM,” and an enrollment of 4. Allocation is NA and masking is NONE. The phase is listed as NA, and the kind is recorded as other. These entries describe a device evaluation rather than a randomized treatment comparison. In particular, there is no listed control arm from which to estimate a between-group effect.
The brief summary describes a project that would evaluate the Smart Wheelchair Component System for power wheelchairs and the Smart Power Assistance Module for manual wheelchairs in realistic indoor environments. It distinguishes group trials involving individuals with visual impairment but no mobility impairment from several single-case studio activities involving individuals with visual and mobility impairment. The record does not explain how these activities were allocated to the listed arm, how many participants were involved in each activity, or whether all participants used both devices. Those details are not reported in the registry record.
The recorded start date is 2006-06, and the primary completion date is 2008-05. The status is COMPLETED. These administrative entries do not establish that the primary outcome was collected: the primary outcome entry explicitly states, “No data was collected.” Nor does the completed status itself indicate that the devices were successful, that the intended evaluation was fully carried out, or that a formal analysis occurred.
The record lists one primary outcome measure and zero analyses. It does not report a statistical analysis plan, participant flow, device-use sequence, or baseline measurement. The design should therefore be read as a small, single-group project record with a stated indoor-course outcome and a missing outcome result, rather than as an efficacy comparison. The project’s long-term objective was to provide independent mobility to veterans with mobility and sensory impairments, but that objective is not itself an outcome demonstrated by this record.
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
| Stage | Arm 1: SWCS and SPAM |
|---|---|
| STARTED | 4 |
| COMPLETED | 0 |
| NOT COMPLETED | 4 |
Analysis population for the primary outcome, as defined in the registry: No data was collected.
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.
| Characteristic | Unit | Arm 1: SWCS and SPAM |
|---|---|---|
| Participants analysed | 4 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 4 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 4 |
| Region of Enrollment: United States | participants | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Time to Complete Trial Wheelchair Course, measured over Two years.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is titled “Time to Complete Trial Wheelchair Course.” It is a measure of elapsed time for a user to travel through a configured indoor course. The description specifies a research-laboratory setup with a straight path and 90 degree turns, along with obstacles such as a cardboard box, a large orange cone, and a desk chair. Obstacle locations were randomly placed to test whether SPAM or SWCS could detect objects. The timeframe is given as “Two years.”
Completion time is a direct performance measure: it records how long a course takes rather than asking a participant to rate ease of use or confidence. In general, timed task measures can capture the combined consequences of navigating a route, responding to obstacles, and completing turns. They do not by themselves identify why a course took a particular length of time. For instance, a time value alone would not distinguish cautious travel from difficulty detecting an obstacle unless additional measures or observations were also collected.
The registry record does not report a unit, a specific endpoint parameter, or a measure of dispersion. More importantly, it says no data were collected. There is consequently no posted completion time, distribution, or comparison to interpret. The outcome description clarifies the planned measurement and environment, but it cannot be treated as evidence that either device detected obstacles or changed course performance.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central interpretive fact is that the registry record names a primary endpoint but reports no collected data for it. There is no completion-time estimate, no account of observed variation, and no analysis of the intended measure. The record therefore gives no quantitative evidence about how participants performed on the course. A study marked COMPLETED can still have no result available for a particular outcome; completion status should not be substituted for outcome evidence.
The design also limits what a result could establish even if a course time had been reported. The record describes a single group and one arm that names both SPAM and SWCS. Allocation is NA, and the listed arm structure does not provide a like-for-like control comparison. Without an explicit comparator, a course time could describe performance in the study setting, but it would not by itself show what performance would have been without the device or with a different device. The registry record does not explain whether the two systems were evaluated separately, in sequence, or with different participant groups.
The project summary describes two types of activities: group trials with people who had visual impairment without mobility impairment, and single-case studio work with people who had both visual and mobility impairment. The record does not give separate outcome data or participant descriptions for these activities. It is therefore not possible to determine which activity the listed enrollment covers, how well it represents either target group, or whether the course outcome was obtained in each context. The listed conditions—blindness and spinal cord injury—do not fill in those missing details.
The sample-size assumptions attached to planning illustrations are not findings from the trial. They describe a hypothetical planning approach based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The record does not report an observed primary-outcome effect from which to assess those illustrations, nor does it give a trial-specific design justification. These assumptions should not be read as evidence of observed power, as a description of the actual single-group design, or as a result of a registered analysis.
Zero affected participants are recorded for both serious and other adverse events among 4 participants at risk in the listed arm. These entries describe the safety counts in the registry record, not a complete characterization of risk. Deaths are not reported in the registry record. The safety entries do not supply the missing course outcome and cannot answer the primary performance question.
In short, the record documents the intended device evaluation and course measure, but not the outcome evidence needed to quantify performance. No conclusion about device benefit, lack of benefit, or comparative performance follows from the absence of posted outcome data.
9. Statistical Methods Explained
What does a single-group design tell the reader?
In general, a single-group design describes observations made in one study group rather than estimating a contrast between randomized groups. If an outcome is collected, it can characterize what happened under the conditions recorded. It cannot, on its own, separate the intervention's contribution from other influences or show what would have happened to the same participants under a different condition. That distinction matters for the present record: the listed model is SINGLE GROUP, the arm is “SWCS and SPAM,” and allocation is NA. No like-for-like control comparison is described.
A single-group project may include different procedures or participant experiences, but the record must describe them clearly to support comparisons. The brief summary refers to group trials and single-case studio work, while the registry lists one arm. The record does not say how the listed devices correspond to each activity, or whether participants used one or both. It would therefore be inappropriate to infer a crossover design, a device-by-device comparison, or a particular sequence of use.
What does a course-completion time measure?
In general, a time endpoint is a quantitative measure of task duration. It can be useful when completing a defined task is the performance of interest. Its meaning depends on a consistent start point, end point, route, and measurement procedure. This registry description identifies a laboratory course, a straight path, turns, and obstacles placed at random locations. It states that time was recorded and that the setup was intended to test object detection. The record does not report the unit, the specific endpoint parameter, or details of the timing procedure. It also reports no collected outcome data, so the endpoint cannot be summarized numerically.
Time and object detection are related but not interchangeable concepts. A course time could reflect navigation speed and task completion, while detection concerns whether an obstacle is recognized. A time measure alone does not indicate the accuracy of detection or explain a delay. General interpretation of a timed endpoint would therefore benefit from supporting measures or clear operational details, but those are not reported in the registry record.
How should the planning assumptions be read?
The registry record describes planning illustrations based on an observed effect. It lists a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. It also distinguishes time-to-event planning, which gives a total number of events under the Schoenfeld approach, from other outcomes, which give participants per arm.
These are planning conventions, not results. A sample-size illustration answers a hypothetical question about what a future design might require under specified assumptions. It does not describe how many participants were actually analyzed, nor does it establish the power achieved in this project. In particular, the equal-allocation, two-arm assumption differs from the registry's single-group model and one listed arm. The illustrations should not be treated as the documented design of this study. The record does not report the protocol's sample-size justification or explain how the assumptions were selected.
In general, a significance level sets a thresholding convention for a statistical test, and a normal approximation uses a mathematical distribution to approximate a sampling distribution. A stated fraction of an effect can be used to explore sensitivity to smaller target effects. Such assumptions can be useful when planning a future study, but they do not create evidence of an effect in a study with no reported primary outcome data. No numerical sample-size result or observed effect is reported in the registry record.
Why do uncertainty and analysis details matter?
In general, a confidence interval describes a range of values compatible with the data and the statistical procedure, and communicates precision as well as direction. A narrow interval indicates greater precision than a wide interval under the same method. A test result or point estimate without an interval can leave uncertainty difficult to judge. Here, no primary-outcome estimate or interval is reported, so precision cannot be assessed. The registry record also lists zero analyses. It does not report a statistical model, handling of repeated measurements, or an analysis plan.
For time outcomes, methods should match how the data were collected. A simple average, a median, or a time-to-event analysis can answer different questions and relies on different assumptions. General methods for time-to-event outcomes may account for participants who do not experience the event during observation, whereas a course-completion time is not automatically a time-to-event outcome. The record's sample-size note mentions a Schoenfeld approach for time-to-event planning, but the primary endpoint is described as time to complete a course. The note does not establish that a time-to-event analysis was planned or used for this endpoint.
General statistical methods also need to account for clustering or over-dispersion when observations are more variable or dependent than a simple model assumes. Those issues cannot be assessed without outcome data and a clear account of the data structure. The record does not report repeated observations, a model, or a measure of dispersion. A sound interpretation must leave these questions open rather than infer an analysis from the endpoint title or planning assumptions.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one primary outcome measure and zero analyses. It does not report a statistical analysis plan, so any planned handling of multiple outcomes, repeated measurements, or multiple comparisons is not reported in the registry record. There is no basis in the record to claim that a multiplicity adjustment was applied, or that one was unnecessary. The listed project activities and two device names do not, by themselves, establish how many comparisons were planned or performed.
In general, multiplicity arises when several statistical questions are tested or estimated and the collection of results is interpreted together. Repeated testing can increase the chance of a misleading finding if the analysis does not account for the family of questions. Researchers may define one primary outcome, specify a testing hierarchy, adjust thresholds, or emphasize estimates and uncertainty. Which approach is appropriate depends on the design and analysis plan. No such approach is described in this registry record.
The record says no data were collected for the primary outcome. This is more direct than a conventional missing-data situation in which some participants have outcomes and others do not: no primary endpoint data are reported as collected. The record does not explain whether data were unavailable, not measured, or excluded, and it does not describe imputation or other missing-data methods. Those details are not reported in the registry record.
Analysis populations are also not described. The enrollment entry is 4, but the record does not identify who was included in any outcome analysis or whether an analysis population was defined. The zero analyses entry and absence of outcome results mean there is no reported participant-level analysis to evaluate. No intention-to-treat, per-protocol, or other analysis population should be inferred.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Arm 1: SWCS and SPAM | 0 | 4 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Arm 1: SWCS and SPAM | 0 of 4 |
The listed arm is “SWCS and SPAM.” The registry records 4 participants at risk for serious adverse events and 0 affected. It also records 4 at risk for other adverse events and 0 affected. These entries indicate that no affected participants are recorded in either category for the listed arm. They should be read as the registry's reported counts, not as proof that the devices have no risks or that every possible adverse event was systematically assessed.
The deaths field is null, so a death count is not reported in the registry record. A blank or null entry is not the same as a recorded count of zero. The record does not provide event terms, follow-up duration for safety monitoring, or additional detail about how adverse events were defined or collected. The serious adverse event terms list is empty, which does not add detail about ascertainment.
Safety counts are distinct from the primary performance outcome. They do not provide course-completion times or answer whether obstacles were detected. With the small enrollment recorded and no outcome data collected, the safety entries offer only a limited account of what is recorded for this study, not a broad estimate of event frequency or risk.
12. What the Result Does, and Does Not, Mean
The record establishes that a device project was registered and marked completed, that it listed SPAM and SWCS, and that its primary outcome was time to complete an indoor wheelchair course. The course description gives concrete context: a straight path, 90 degree turns, and randomly placed obstacles including a cardboard box, a large orange cone, and a desk chair. The project focused on independent mobility for people with visual and mobility impairments, with a long-term objective concerning veterans with those impairments.
What the record does not establish is the measured performance of either device. It explicitly says no data were collected for the primary outcome. No completion-time value, comparison, uncertainty estimate, or analysis is reported. The registry does not show whether a participant completed the course, how obstacles were handled, or whether performance differed across devices or participant groups. The listed arm combines both device names and no control arm is described.
Accordingly, the record cannot support a conclusion that SPAM or SWCS improved mobility, reduced course time, detected obstacles, or performed differently from another approach. It also cannot support the opposite conclusion that the devices failed to do so. Lack of outcome data is not evidence of no effect; it is an absence of a reported estimate. General statistical reasoning requires separating a missing result from a result that is close to no difference or that is imprecise.
The safety entries record zero affected participants for serious and other adverse events among 4 at risk in the listed arm, while deaths are not reported in the registry record. These counts are useful as a description of the posted safety information, but they do not resolve the primary question or establish safety beyond the recorded information.
The appropriate takeaway is narrow: the registry documents an intended evaluation and its setting, but does not report the outcome evidence needed to determine performance. The study's completion status, planning assumptions, and stated long-term objective should not be mistaken for measured effects.
13. Why This Trial Matters Statistically
This record is statistically informative in part because it illustrates the difference between a registered question and an available result. A clearly described endpoint can identify what investigators intended to measure, while still leaving the effect and its precision unknowable when no outcome data are reported. Readers should distinguish the existence of an outcome definition from the existence of an outcome estimate.
It also highlights the importance of matching statistical interpretation to design. A single-group record with allocation listed as NA does not provide a randomized comparator. Even if a course time had been posted, the absence of a control group would constrain causal interpretation. The summary describes different user groups and activity types, but the registry does not connect those details to a separate analysis structure. Transparent reporting of participants, device exposure, and outcome collection is necessary to understand what a result represents.
The course endpoint points to a practical measurement challenge. Completion time is straightforward to describe, but it can combine several aspects of navigation and task performance. The record's obstacle-detection objective is not identical to a time measure, so a strong evaluation would need a clear account of what was assessed and how. This is a general design consideration, not evidence that any additional measure was collected in this study.
Finally, the planning note is a reminder that sample-size calculations depend on assumptions and are not study results. The stated planning approach invokes two arms and equal allocation despite the registered single-group model. Treating such illustrations as a description of the trial would conflate hypothetical planning with the design actually recorded. The record therefore underscores the value of keeping design, planning, observed data, and analysis distinct when interpreting clinical research.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most important limitation is explicit: no data were collected for the primary endpoint. Without time measurements, the registry cannot provide an estimate of course performance or its precision. The outcome description does not remedy the absence of results.
The design record is also sparse. It lists a single-group model, one arm combining SPAM and SWCS, allocation as NA, and masking as NONE. It does not explain whether the devices were assessed separately, whether all users encountered both systems, or how the group trials related to the single-case studio work in the project summary. These details are not reported in the registry record, so comparisons between systems or participant types cannot be reconstructed.
The enrollment entry is 4, but participant characteristics, distribution among the described activities, and analysis populations are not reported. The conditions listed do not specify the degree of visual or mobility impairment, wheelchair type, or other characteristics needed to interpret applicability. Such details should not be inferred from the condition labels or project goals.
The endpoint description gives the course environment and obstacle examples, but does not report a unit, an endpoint parameter, a dispersion measure, or the timing procedure. Nor does it specify an outcome directly quantifying object detection. The timeframe is recorded as “Two years,” but the record does not clarify how this applies to individual outcome collection.
There are zero analyses listed, and the statistical analysis plan, missing-data approach, and multiplicity strategy are not reported in the registry record. The planning assumptions describe a hypothetical two-arm approach and should not be treated as the trial's analysis plan. Safety information is also limited: deaths are not reported in the registry record, and no further event-collection details are given. Together, these gaps sharply limit interpretation beyond the stated study aim and record entries.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Use of "Smart Wheelchairs" to Provide Independent Mobility to Visual and Mobility Impairments — NCT00333762.
- Registry record last updated 2015-12-03; status last verified 2015-10.
- Results first posted 2015-12-03.
- 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.
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Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
NCT00333762 is a completed device study sponsored by the VA Office of Research and Development. The registry describes a single-group model with one arm named “SWCS and SPAM,” an enrollment of 4, allocation listed as NA, and masking listed as NONE. The project concerned smart wheelchair systems for indoor mobility and included a stated long-term objective of independent mobility for veterans with mobility and sensory impairments.
The primary outcome was time to complete an indoor wheelchair course with turns and randomly placed obstacles. The record states that no data were collected, and it lists zero analyses. Consequently, no course-time result or statistical estimate is reported. Serious and other adverse event counts each list 0 affected among 4 at risk; deaths are not reported in the registry record. The available information supports description of the registered aim and design, but not an estimate of device performance.