Promoting Physical Activity in Rural Communities: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Promoting Physical Activity in Rural Communities (NCT03683173), a randomized na study. The primary outcome is Change in Objective Physical Activity Measured by Accelerometer Measured at Baseline and 18-month Follow-up.

2. Clinical Question

The study focuses on physical activity in rural communities and tests an approach operating at more than one level. The intervention components include activities intended to engage communities and support walking groups, as well as short messaging service. The registry’s expectation about greater participation is a statement of the study’s rationale, not a result.

The primary question is about change in an objectively measured activity outcome over follow-up. The record also lists a secondary outcome concerning whether participants met subjective physical activity recommendations, assessed with the Global Physical Activity Questionnaire at baseline and 18-month follow-up. It does not report results for that secondary outcome. The endpoint description and the small number of participants with valid paired primary-outcome data are important context when interpreting the record.

3. Trial Design

This is a randomized, parallel-group study with no masking. The registry lists the study as completed and names Washington University School of Medicine as the sponsor. The recorded study start date is 2018-12-17, and the primary completion date is 2022-12-24. The phase is listed as NA. Enrollment is recorded as 1241.

Participants were assigned to the Multilevel Intervention or Control group. The intervention is behavioral and consists of community events, walking group formation, and short messaging service. The Control group does not receive the multilevel intervention. Because masking is recorded as none, the registry does not indicate that participants or study personnel were masked to group assignment. The record does not give further details about who knew the assignments or how allocation was implemented.

The parallel design compares groups followed during the same study rather than describing a crossover. Random allocation can support a fair comparison when assignment and follow-up are handled appropriately, but the design label alone does not establish that groups remained comparable in the analyzed data. Missing follow-up measurements, the analysis population, and the statistical handling of missing data matter to that assessment. Those details are not reported in the registry record.

The primary outcome was intended to measure physical activity at baseline and at 18-month follow-up. However, the registry notes that only 56 participants had valid data at both times, with 28 from each group. That is the subset identified for the primary measure, not a reported estimate of treatment effect. No statistical analysis is listed, and no group means, changes, uncertainty intervals, or tests are reported in the registry record. The record does not report the protocol’s sample-size justification or other details of the trial’s statistical plan.

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.

Enrolled and Completed Baseline Survey

Completed Follow-up

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Only 56 participants (28 enrolled in the Multilevel Intervention Arm and 28 enrolled in the Control Arm) had valid data at baseline and at the 18-month follow-up.

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 Change in Objective Physical Activity Measured by Accelerometer Measured at Baseline and 18-month Follow-up, measured over Baseline and 18-month follow-up.

The primary endpoint is change in objective physical activity, measured at baseline and 18-month follow-up. The outcome is weekly minutes of moderate to vigorous physical activity, measured using an accelerometer. The registry describes the summary measure as a mean with standard deviation.

Accelerometers record movement rather than relying on participants to recall or characterize their activity. The registry specifies that activity was classified using the Freedson Adult cutpoint categories from 1998, with counts measured every 60 seconds per minute. Its listed categories range from sedentary and light activity to moderate, vigorous, and very vigorous activity. The primary outcome focuses on moderate to vigorous activity rather than all recorded movement.

Measuring the outcome at baseline and follow-up makes it possible to describe how activity changes over the study period. A comparison of changes between randomized groups could address whether the groups followed different activity trajectories. However, the registry record does not report the group-level measurements or a statistical comparison, so it does not establish the size or precision of any difference in change.

For the primary endpoint, valid measurements at both time points were available for 56 participants, 28 in each group. This paired-data requirement means the primary outcome description applies to that subset. The registry does not report why other participants lacked valid measurements, whether their missingness was related to activity or group assignment, or how missing data were handled in an analysis.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized parallel-group design. Random allocation is intended to create groups that are comparable on average before an intervention begins. In a well-conducted randomized study, comparing outcomes by assigned group can support an estimate of the intervention’s effect. That interpretation still depends on how allocation was implemented, follow-up was maintained, and outcome data were analyzed. Further details of those procedures are not reported in the registry record.

What does the primary summary measure represent?

The primary outcome is continuous: weekly minutes of moderate to vigorous physical activity. A mean describes the average value in a group. A standard deviation describes how dispersed individual measurements are around that group mean. These summarize different features: the mean locates the group’s average, while the standard deviation indicates variability among measured participants. The registry identifies these summary measures but does not report their values.

The endpoint is measured at baseline and 18-month follow-up, and the title describes change between those times. A group’s change can describe how its measured activity differs across assessments. To answer the randomized comparison, the analysis would need to define how change is compared across groups, or otherwise specify a model that uses the repeated measurements. The registry record does not report the analysis model or a numerical comparison. No particular method, such as an analysis of change scores or a repeated-measures model, should be assumed.

How should uncertainty be understood?

General statistical explanation: a confidence interval conveys the precision of an estimated quantity under the assumptions of the analysis. A relatively wide interval indicates that the estimate is compatible with a broader range of values; a narrower interval indicates greater precision. A p-value is tied to a specified null hypothesis and analysis model. Neither measure substitutes for the estimated effect itself, and neither is reported for the primary outcome in the registry record.

For a continuous outcome, an analysis may account for baseline measurement, follow-up measurement, and variation between participants. But the exact statistical plan is not reported. It is therefore not possible to determine whether the reported outcome was intended to be analyzed as a change score, by adjustment for baseline, or using another approach. The record also does not report whether any covariates were planned or used.

What does the sample-size note mean?

The registry’s planning note describes an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Such calculations are planning illustrations: they describe sample-size requirements under stated assumptions, not the probability that this completed study detected an effect. They are not observed power.

The registry record does not report the trial’s own sample-size justification or statistical plan. It also does not report a numerical primary-outcome effect from which to assess the planning assumptions. No planning sample-size values are stated in the record. The note’s distinction between participants per arm for non-time-to-event outcomes and total events for time-to-event calculations is general to the planning description; the primary endpoint is continuous, not time-to-event.

Why does the measurement subset matter?

The registry reports valid primary-outcome measurements at both time points for 56 participants, with 28 in each group. An analysis based on participants with both measurements can be affected if the availability of valid data is related to group assignment, activity, or other factors. This is a general missing-data concern, not a claim that such a pattern occurred in this study. The registry does not describe why records were unavailable, whether incomplete observations were included in any model, or whether a sensitivity analysis was performed.

Since the record lists zero analyses and does not give outcome summaries, there is no basis for recalculating an effect from posted summary statistics. No recalculated estimate, standard error, confidence interval, or p-value can be derived from the registry record. The statistical conclusion must remain that the intended comparison is identifiable, but its result and precision are not reported.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome description refers to measurements at baseline and 18-month follow-up and to several activity categories. The registry’s skip note states that the primary outcome has several categories or time points and was not reduced to one comparison. This matters because an outcome measured across multiple times or categories can support more than one possible comparison. A statistical plan normally clarifies which comparison is primary and how any additional analyses will be handled. Such a plan is not reported in the registry record.

The registry lists zero analyses. It does not report a multiplicity adjustment, a hierarchy of outcome tests, or a prespecified method for choosing among time points or activity categories. Without those details and without outcome estimates, the risk of selective emphasis across possible comparisons cannot be assessed. This does not establish that selective reporting occurred; it means the record does not provide information to evaluate it.

Missing outcome data are also material. Only 56 participants are described as having valid primary-outcome data at both baseline and 18-month follow-up, with 28 in each group. The registry does not state why the remaining enrolled participants lack paired valid measurements, whether all were assigned to a group, or whether missingness differed for reasons related to group or outcome. It does not report an imputation method, a missing-data model, or sensitivity analyses.

The analysis population is not specified beyond the description of the valid-data subset. The record does not say whether the intended analysis followed original group assignment for all randomized participants, used only participants with available measurements, or applied another population definition. As a result, the effect of missingness and the relationship between the enrolled population and the primary-outcome analysis population cannot be evaluated from the registry record.

11. 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 serious adverse events and other adverse events as counts by group, alongside the number at risk. For the Multilevel Intervention group, 627 participants are listed as at risk for both categories; serious adverse events are 0 and other adverse events are 0. For the Control group, 614 are listed as at risk for both categories; serious adverse events are 0 and other adverse events are 0. These are the event counts recorded in the registry.

Deaths are listed separately: 5 in the Multilevel Intervention group and 4 in the Control group. The registry does not describe whether those deaths were considered related to the intervention, nor does the record give circumstances or timing. The counts alone do not establish a causal relationship. They also should not be conflated with the listed serious or other adverse event counts.

General statistical explanation: counts describe how many events were recorded, while rates require a defined time at risk and a rate calculation. The registry figures should be read as reported counts, not as comparative rates. The record does not provide a statistical comparison of safety outcomes or enough detail to assess differences in exposure time. These figures therefore describe the recorded safety entries without establishing comparative safety conclusions.

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

The record documents a randomized study of a multilevel approach to promoting physical activity in rural communities. It specifies an intervention involving community events, walking group formation, and short messaging service, alongside a Control group that does not receive that intervention. It also defines an objective primary outcome based on accelerometer-measured weekly minutes of moderate to vigorous activity at baseline and 18-month follow-up.

What the record does not establish is whether the intervention changed physical activity relative to control. The primary outcome’s group summaries and comparison are not reported, and the registry lists zero analyses. There is no reported estimate of effect, confidence interval, or p-value. Accordingly, the record cannot support a conclusion about the direction, magnitude, or precision of a difference between groups.

The 56 participants with valid data at both measurement times, including 28 in each group, are the population identified for the primary outcome. That information does not reveal the outcome values, the reasons data were missing for other participants, or whether the valid-data subset is representative of the enrolled population. It also does not determine whether the study had adequate precision for its primary question.

The registry’s stated expectation that more participation in the intervention could be associated with greater activity is a rationale, not a finding. Likewise, the completion status and recorded enrollment do not supply an outcome result. The secondary questionnaire-based measure is listed but has no reported result in the registry record.

In practical statistical terms, this is a record of the study question and design rather than a report of its primary comparative finding. No treatment recommendation follows from the registry information. A complete interpretation would require the outcome summaries, analysis specification, uncertainty estimates, and details of the analysis population and missing data; those are not reported in the registry record.

13. Why This Trial Matters Statistically

This study is statistically notable for the gap between its recorded enrollment and the much smaller number with valid primary-outcome measurements at both assessment times. Enrollment is 1241, while the primary endpoint description identifies 56 participants with valid baseline and 18-month data, with 28 in each group. That distinction illustrates why enrollment alone does not indicate how much information contributes to a particular outcome analysis.

The endpoint also raises a common design and analysis issue: physical activity is measured repeatedly and classified into activity categories, while the primary question concerns change over time. Such data require a clear definition of the target comparison. The registry notes that the primary outcome has several categories or time points and was not reduced to one comparison. Without a specified contrast and reported analysis, readers cannot identify which result would answer the primary question.

Objective measurement is another relevant feature. Accelerometer data offer a measurement approach different from self-report, while the listed secondary measure uses a questionnaire. These outcomes may capture physical activity in different ways, but the registry provides no results to compare their findings. A planned comparison between objective and subjective measures, if any, is not reported in the registry record.

Finally, this record demonstrates the limits of interpreting a completed trial when outcome analyses are absent. Randomization and a defined endpoint describe the intended evidential structure, but conclusions require observed estimates and their uncertainty, alongside a transparent account of missing data and analysis choices. The registry supports a clear description of the research question and measurement plan, but not a statistical conclusion about the intervention’s effect.

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 direct limitation for interpretation is that the registry record does not report primary-outcome results. No group means, changes, between-group effect estimate, confidence interval, or p-value are listed, and the record lists zero analyses. Therefore, the intended comparison cannot be evaluated statistically from the registry entry.

The primary endpoint is available for only the subset described as having valid data at both baseline and 18-month follow-up: 56 participants, with 28 in each group. The reasons for missing or invalid measurements are not reported. The record also does not explain whether the analysis would include participants without complete measurements or how missing data would be handled. This limits assessment of both precision and potential bias.

The outcome involves multiple activity categories and assessment times, and the registry explicitly says it was not reduced to one comparison. The record does not identify a single analysis contrast, a multiplicity strategy, or a statistical model. It does not report whether the analysis accounted for baseline values, covariates, or other design features. These omissions make it impossible to determine how the primary question was operationalized analytically.

The study is recorded as unmasked, but further details about allocation procedures, follow-up, adherence, or implementation are not reported in the registry record. The intervention expectation mentions participation at different levels, while the listed intervention and control descriptions do not provide results by level of participation. No conclusion about adherence or differences in participation can be drawn.

Finally, although the record is marked completed, completion status does not substitute for results. The registry does not report a sample-size justification or enough outcome information to assess whether the study could estimate the intended effect precisely. These limitations describe the information available in the registry record, rather than asserting that the underlying study lacked analyses or additional data.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Promoting Physical Activity in Rural Communities — NCT03683173.
• Registry record last updated 2024-01-08; status last verified 2024-01.
• Results first posted 2024-01-08.
• 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.

18. Record Summary

NCT03683173, Promoting Physical Activity in Rural Communities, is recorded as a completed randomized parallel-group study with no masking. The sponsor is Washington University School of Medicine. Enrollment is 1241. The intervention consists of community events, walking group formation, and short messaging service; the Control group does not receive the multilevel intervention.

The primary endpoint is change in accelerometer-measured weekly minutes of moderate to vigorous physical activity from baseline to 18-month follow-up. The registry identifies 56 participants with valid data at both times, 28 in each group. It lists a secondary questionnaire-based physical activity outcome, but no outcome analyses are reported. The primary result, its uncertainty, the analysis population, and the missing-data approach are not reported in the registry record.