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 Effects of Installing Height-adjustable Workstations on Office Workers Workplace Sitting Time and Productivity (NCT02932787), a randomized na study. The primary outcome is Change in Workplace Sedentary Time.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02932787 |
| Phase | NA |
| Condition | Workplace Inactivity |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 31 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sheffield Hallam University |
| Results posted | Yes |
2. Clinical Question
Population
Desk-based office workers; the registry record lists 31 participants enrolled. The condition is workplace inactivity.
Intervention
Participants in the intervention arm received a height-adjustable workstation for four weeks.
Comparator
The control group received no intervention. The record does not give a further description of the control condition.
Primary question
What change in workplace sedentary time was recorded from baseline to four weeks after workstation installation, and how did that change compare between the intervention and control groups?
The study also listed workplace absenteeism and presenteeism, assessed using the World Health Organisation Health and Work Performance Questionnaire, as secondary outcomes. The registry record does not report the results for these measures or the primary outcome. It therefore does not establish the size or direction of any between-group difference, or how precise an estimate might be.
3. Trial Design
This was a randomized, parallel-group study with no masking, listed as completed. The registry record gives an enrollment of 31 and identifies height-adjustable workstations as the intervention. Participants in that arm received a workstation for four weeks; the control group received no intervention. The record describes workplace activity and productivity being measured before workstation installation and again four weeks later.
The stated study dates are 2013-12 for the start and 2015-11 for primary completion. The phase is listed as NA. The sponsor was Sheffield Hallam University. These descriptive details identify the trial structure and its setting in time, but do not tell readers how participants were recruited, how randomization was generated or concealed, or whether allocation was balanced in practice. Those details are not reported in the registry record.
The primary endpoint is change in workplace sedentary time, expressed in minutes and described as a mean with standard deviation. Sitting time was measured using a thigh-worn ActivPAL accelerometer. The registry record names absenteeism and presenteeism as secondary outcomes, but does not provide their results or detailed measurement schedules.
No analysis is listed in the registry record. That absence means the record does not provide an estimate of the intervention-control contrast, a confidence interval, or an inferential test for the primary endpoint. The design description alone cannot show whether the workstation changed sitting time or whether a difference would be distinguishable from sampling variation.
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 | Height-adjustable Workstation | Control |
|---|---|---|
| STARTED | 22 | 9 |
| COMPLETED | 22 | 9 |
| NOT COMPLETED | 0 | 0 |
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 | Height-adjustable Workstation | Control | Total |
|---|---|---|---|---|
| Participants analysed | 22 | 9 | 31 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 22 | 9 | 31 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 46 (SD 10.3) | 37 (SD 7.26) | 43.38 (SD 9.42) |
| Sex: Female, Male: Female | Participants | 12 | 7 | 19 |
| Sex: Female, Male: Male | Participants | 10 | 2 | 12 |
| Region of Enrollment: United Kingdom | Participants | 22 | 9 | 31 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Workplace Sedentary Time, measured over Baseline (0 weeks), 4 weeks after installation of height-adjustable workstations.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | Minutes |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change in workplace sedentary time, measured in minutes. The registry description defines this as the amount of time a participant spends sitting while at work. A thigh-worn ActivPAL accelerometer was used for measurement. The stated assessment points are baseline, at 0 weeks, and 4 weeks after installation of the height-adjustable workstations.
In general, a change endpoint compares a later measurement with a baseline measurement. It can describe whether sitting time increased or decreased over the study period, while a comparison between randomized groups can help distinguish changes associated with the intervention from changes also seen in the control group. The endpoint’s use of minutes makes it a continuous measure; reporting a mean and standard deviation describes its central value and variability across participants.
The registry record does not provide the group means, standard deviations, changes, or a between-group estimate. It also does not report the specific rule used to calculate change or how incomplete measurements were handled. As a result, the endpoint’s intended meaning is clear, but its observed result and precision cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a randomized comparison of a four-week height-adjustable workstation intervention with a control group receiving no intervention. Its primary question concerns change in workplace sitting time between baseline and the four-week assessment. However, the posted record does not include numerical results for that endpoint and lists no analyses. There is therefore no reported estimate from which to describe the direction or magnitude of the group difference.
For a continuous endpoint, a useful interpretation would ordinarily distinguish the observed group changes from the contrast between those changes. The group-level summaries would show what happened within each arm; the between-group estimate would address whether the changes differed. A confidence interval would express the uncertainty around that estimated contrast. None of these outcome statistics is reported in the registry record, so neither the observed difference nor its precision can be characterized.
The record lists 31 participants enrolled. It also gives safety denominators of 22 for the height-adjustable workstation group and 9 for the control group. These figures describe the recorded groups for adverse-event reporting; they do not supply the missing primary-outcome summaries or clarify the number with complete endpoint measurements. The registry record does not report the analysis population or missing-outcome handling.
The study also lists changes in workplace absenteeism and presenteeism as secondary outcomes, measured with the World Health Organisation Health and Work Performance Questionnaire. Their numerical results are not reported in the registry record. The record identifies three outcome measures and zero analyses, and notes that the primary outcome has several categories or time points and was not reduced to one comparison. Thus the available entry does not support a complete statistical interpretation of any endpoint.
In general, a lack of a posted estimate is not evidence that the groups were the same, and it is not evidence that they differed. It means the registry record does not contain the result needed to make either statement. The design can frame a comparison, but design information alone cannot replace outcome data.
9. Statistical Methods Explained
The registry record describes a randomized, parallel-group trial. In general, randomization is intended to make treatment assignment independent of participants’ characteristics, on average, so that group comparisons can be interpreted as comparisons of assigned strategies. It does not guarantee that every baseline characteristic will be balanced in a particular trial. The record does not describe the randomization sequence, allocation concealment, or baseline characteristics.
What does a change endpoint represent?
The primary measure is continuous: workplace sedentary time in minutes, summarized using a mean and standard deviation. A change measure relates a participant’s follow-up measurement to their baseline measurement. A group comparison may then examine whether average change differs between the workstation and control arms. This is a general description of how such endpoints can be analyzed; the registry record does not state the exact calculation or statistical model used for this trial.
A mean gives a measure of the center of a distribution, while a standard deviation describes the spread of individual values around that mean. Neither quantity alone gives the uncertainty of a treatment contrast. A confidence interval around a contrast is generally used to show a range of values compatible with the data and the analysis assumptions. No means, standard deviations, contrasts, or confidence intervals are reported in the registry record.
What can a randomized comparison show?
In general, the key estimate for a two-arm study is a contrast between the assigned groups, rather than a conclusion drawn only from whether one group changed from baseline. Both groups can change over time for reasons unrelated to the intervention. Comparing their changes helps account for such common change, subject to the study’s design and analysis assumptions. The registry record does not report a contrast or identify an analysis model, so it is not possible to explain how the trial’s investigators estimated the primary effect.
Statistical significance testing, when used, addresses how compatible observed data are with a specified statistical null hypothesis under a model. A p-value is not a measure of effect size, and a result that does not cross a chosen threshold does not establish that effects are absent. The registry record does not report a p-value, significance threshold for the trial’s own analysis, or hypothesis-testing plan.
Why do uncertainty and distribution matter?
In general, the standard deviation describes variation among measurements, while the standard error describes uncertainty in an estimated quantity. They answer different questions and should not be treated as interchangeable. Continuous measures can also have distributions that are skewed or contain influential observations. Whether those features were assessed, and whether any alternative methods were used, is not reported in the registry record.
Over-dispersion is a general concern most often discussed for count outcomes: it occurs when observed variability exceeds what a chosen model assumes. It is not a reported feature of this trial’s primary continuous endpoint. The registry record does not describe diagnostics or model assumptions, so no claim can be made about whether distributional issues affected the analysis.
What do the planning assumptions mean?
The record describes planning illustrations based on a fraction of the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are planning assumptions, not a report of the trial’s own design justification or an observed-power calculation. The stated effect is not reported as a primary-outcome result in the registry record, and no planning sample-size values are given in the record. The trial’s sample-size justification is not reported in the registry record.
In general, a sample-size calculation asks how many participants would be needed under specified assumptions about effect size, variability, allocation, and error rates. An illustration based on an observed effect is conditional on that assumed effect and should not be read as evidence that a trial had adequate power. The record does not report an interim-analysis plan, stopping rule, or other statistical design details.
10. Multiplicity, Missing Data and Analysis Populations
The registry record identifies a primary outcome and two secondary outcomes: workplace absenteeism and workplace presenteeism, both assessed using the World Health Organisation Health and Work Performance Questionnaire. It lists three outcome measures and zero analyses. The primary outcome is described as having several categories or time points and was not reduced to one comparison. No single primary contrast or numerical outcome result is reported.
When several outcomes, time points, or statistical tests are examined, the chance of at least one apparently notable result can increase. In general, multiplicity procedures may adjust how results are interpreted or tested. The registry record does not report whether any multiplicity adjustment was planned or used. It also does not report a statistical analysis plan from which the intended hierarchy of outcomes or comparisons could be determined.
The record does not state how missing baseline or follow-up measurements were handled, whether all randomized participants were included in an analysis, or how the analysis population was defined. These details are important because the number enrolled is not necessarily the number contributing data to each endpoint. The registry record lists 31 participants enrolled, but does not give endpoint-specific completion counts or reasons for missing data.
Without those details and the outcome estimates, readers cannot assess the effect of missing measurements, determine whether the listed secondary outcomes were analyzed, or establish how the study addressed multiple comparisons. These methods and analysis-population details are not reported in the registry record.
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 |
|---|---|---|---|
| Height-adjustable Workstation | 0 | 22 | 0.0% |
| Control | 0 | 9 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Height-adjustable Workstation | 0 of 22 |
| Control | 0 of 9 |
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 |
|---|---|
| Height-adjustable Workstation | 0 of 22 |
| Control | 0 of 9 |
The adverse-event record lists the height-adjustable workstation group with 22 participants at risk and zero serious adverse events, zero other adverse events, and zero deaths. The control group is listed with 9 participants at risk and zero serious adverse events, zero other adverse events, and zero deaths. No serious adverse-event terms are listed.
These are event counts and reported denominators, not estimates of the probability of harm. A count of zero means no event of that category was recorded in the listed group in this registry entry; it does not establish that an event could never occur. The record does not give the safety observation period, definitions of adverse events, collection procedures, or a narrative explaining how events were monitored.
In general, safety counts are interpreted in light of the number observed, the duration of observation, and how events were sought and classified. The registry record’s safety figures do not resolve those questions. They should also be kept separate from the primary endpoint: the absence of recorded adverse events does not provide information about changes in workplace sitting time.
12. What the Result Does, and Does Not, Mean
The study description addresses a practical statistical question: whether workplace sitting time changed differently over four weeks for participants receiving height-adjustable workstations compared with a control group receiving no intervention. The registry record identifies the population, intervention, comparator, measurement instrument, and intended primary endpoint. It does not report the primary outcome values or any analyses.
Because no group summaries or estimated contrast are reported, the direction and size of the observed difference are unknown from this record. There is also no confidence interval or other uncertainty measure with which to judge precision. A randomized design by itself does not supply these missing results. It describes how the comparison was intended to be formed, not what the measured outcome showed.
The record also does not report results for absenteeism or presenteeism. Consequently, the registry entry cannot establish whether those measures changed, whether changes differed by group, or how precise any such estimates were. The zero adverse-event counts are limited to the categories and denominators recorded; they do not answer the primary endpoint question.
In general, a statistically non-significant result, if reported, would not by itself prove no effect; similarly, a statistically significant result would not by itself convey the size or practical importance of a difference. Here, the necessary results are not reported in the registry record, so neither kind of inference is available. No conclusion about benefit or lack of benefit should be drawn from the design description or the absence of posted analyses alone.
The registry entry is therefore informative about the study’s intended comparison and measurement schedule, but incomplete for interpreting outcomes. Its central statistical limitation is not a particular estimate with wide or narrow uncertainty; it is that no estimate or uncertainty measure is reported.
13. Why This Trial Matters Statistically
This trial illustrates why a clear endpoint definition and an interpretable estimate are both needed. The registry record defines workplace sedentary time in minutes and identifies a thigh-worn ActivPAL accelerometer as the measurement method. It also specifies baseline and a four-week assessment after workstation installation. These details help identify what was intended to be measured and when.
For a randomized study, readers generally need more than the intervention description and enrollment count. They need group-level outcome summaries, an estimate of the between-group contrast, and an indication of uncertainty. Without these, it is not possible to distinguish a substantial difference from a small, imprecisely estimated one, or to assess whether observed changes were similar across the arms. None of those outcome statistics is reported in the registry record.
The record also highlights the importance of transparent reporting about outcome definitions and analysis choices. It identifies secondary productivity measures, but does not report results or explain how multiple outcomes and time points were handled. It gives no analysis population, missing-data approach, or statistical model. Such details allow readers to understand which participants and measurements contributed to an estimate and how the estimate was obtained.
The statistical lesson is that trial design information and outcome evidence serve different purposes. The former describes the intended comparison; the latter is required to evaluate what the measured data show. This registry entry gives the former more clearly than the latter.
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 principal trial-specific limitation for interpreting the registry entry is that no outcome analyses are listed. The primary endpoint is described, but its group means, standard deviations, changes, and between-group comparison are not reported in the registry record. The results for the listed absenteeism and presenteeism outcomes are also not reported. As a result, the trial’s estimated effects and their precision cannot be assessed.
The endpoint description names baseline and four weeks after installation, but the record does not state how participant-level change was calculated or which specific comparison was intended among the several categories or time points. It also does not give endpoint-specific sample sizes, missing-data counts, or reasons for incomplete measurements. Analysis populations and methods for handling missing data are not reported in the registry record.
Further design details relevant to evaluating the comparison are absent: the randomization procedure, allocation concealment, baseline group characteristics, and statistical model are not described. The record does not report a multiplicity strategy, a formal analysis plan, or a sample-size justification for the trial. The planning assumptions described in the record are illustrations, not evidence of the trial’s original design rationale.
Safety interpretation is also limited. Although event counts and denominators are recorded, the safety observation period and event-collection methods are not reported. These limitations concern what can be learned from the registry record; they do not establish that the study itself failed to collect the information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Effects of Installing Height-adjustable Workstations on Office Workers Workplace Sitting Time and Productivity — NCT02932787.
- Registry record last updated 2020-04-28; status last verified 2020-04.
- Results first posted 2020-04-28.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed, randomized, unmasked, parallel-group study sponsored by Sheffield Hallam University. Enrollment was 31. Participants in the intervention arm received a height-adjustable workstation for four weeks; the control group received no intervention.
The primary outcome was change in workplace sedentary time, measured in minutes with a thigh-worn ActivPAL accelerometer at baseline and four weeks after installation. The registry record also lists workplace absenteeism and presenteeism as secondary outcomes. No analyses are listed, and numerical outcome results are not reported in the registry record.
For adverse events, the workstation group lists 22 participants at risk and the control group lists 9; both groups report zero serious events, zero other events, and zero deaths. The record does not report the analysis population, missing-data methods, or statistical model.