Assessment of Chiropractic Treatment Using Reaction and Response Times in Members of the Special Operation Forces (ACT2): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Assessment of Chiropractic Treatment Using Reaction and Response Times in Members of the Special Operation Forces (ACT2) (NCT02168153), a randomized na study. The primary outcome is Simple Reaction Time With the Dominant Hand.

2. Clinical Question

3. Trial Design

ACT2 is identified in the registry as a randomized, single-masked, parallel-group study. Its status is completed, and the recorded enrollment is 120. The listed phase is NA. The sponsor is RAND. The record gives a start date of 2014-08 and a primary completion date of 2016-06.

Participants were assigned to chiropractic manipulative therapy or a wait-list control. The CMT group completed questionnaires and biomechanical assessments and received CMT; the wait-list group completed questionnaires and biomechanical assessments. The registry does not describe the randomization procedure, how allocation was concealed, or which people were masked. “Single” masking is recorded, but the masked role is not identified. The record also does not provide details of the treatment schedule or the wait-list period.

The stated study aim is to evaluate changes in reaction times (RTs) and response times (RespTs) following chiropractic treatment compared with controls in the SFQ population, including Special Operation Forces who are part of the 160th SOAR regiment on flight status. The primary outcome listed for this record is dominant-hand simple reaction time. The registry lists 5 outcome measures and 5 analyses, but the posted primary outcome has multiple categories or time points rather than a single reduced comparison. Numerical outcome estimates and analysis results are not reported in the registry record.

Enrollment describes the number recorded for the trial, not necessarily the number contributing usable observations to a particular outcome analysis. The record notes that early reaction-time data affected by a technical problem were not included in the analysis. It does not state how many participants or measurements were affected. Therefore, the enrollment figure should not be read as the analysis sample size for the primary endpoint.

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 data for the simple hand reaction tests are due to a technical problem in early data collection. Once identified, the problem was corrected. Because data collected before the technical issue was corrected were unreliable and likely inaccurate, they were not included in the analysis for this measure.

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 Simple Reaction Time With the Dominant Hand, measured over Week 1-Study Visit 2, Week 2-Final Visit, Change from Visit 2 to Final Visit.

The primary endpoint is mean simple reaction time with the dominant hand, measured in milliseconds. Handedness is determined by participant self-report. In the task, visual prompts appear on a screen and the participant responds by pressing a button with the thumb of the dominant hand. A set consists of 11 prompts presented in sequence. The time between a response and the next prompt varies from 0.5 to 4.0 seconds in random order. The recorded outcome is the mean time from a prompt appearing to the button press made in response.

Reaction time is used as a measure of the interval between a stimulus and a response. Taking a mean across prompts provides a summary of task performance in the recorded unit, but it can conceal variation among individual responses. The registry specifies the standard deviation as the measure of dispersion. In general, a standard deviation describes how spread out observations are around their mean; it is not itself a measure of the treatment-group difference.

The listed timeframe includes Week 1 at Study Visit 2, Week 2 at the Final Visit, and change from Visit 2 to the Final Visit. These observations allow the endpoint to be considered at the recorded visits and as a change over that interval. The numerical means, standard deviations, and group comparison are not reported in the registry record, so the direction, magnitude, and precision of any change cannot be assessed from this record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the mean represent?

The registry lists the primary endpoint as a mean of a continuous measure, with standard deviation as its dispersion measure. A continuous outcome can take values along a scale rather than being limited to categories. Here, each reaction-time observation is a duration measured in milliseconds, and the endpoint summarizes responses to the visual prompts using their mean. A group mean describes the average observed response time for the observations included in that calculation. It does not show whether every participant had a similar response, and a mean can be influenced by unusually high or low observations.

The standard deviation describes the spread of individual observations around a mean. It is not the uncertainty of the estimated mean or of a between-group contrast. In general, a confidence interval expresses uncertainty about an estimate under the assumptions of the analysis: a narrower interval indicates greater precision, while a wider interval indicates less precision. The registry record does not report standard deviations, confidence intervals, or other numerical estimates for this primary outcome, so those features cannot be evaluated for ACT2 from the posted results.

What is the comparison?

The study uses a parallel design, meaning the treatment groups are followed as separate groups rather than participants crossing from one assigned treatment to another. Randomization assigns participants to the CMT or wait-list group. In general, a randomized comparison can support an estimate of the difference between assigned groups, provided that the outcome data and analysis are handled appropriately. Randomization does not itself specify whether the estimate should compare measurements at a particular visit, compare changes over time, or use another model.

The primary endpoint timeframe names measurements at Study Visit 2 in Week 1, at the Final Visit in Week 2, and change from Visit 2 to the Final Visit. A visit-specific group contrast and a contrast in change answer related but distinct questions. Change comparisons use each participant’s values across visits, so the observations are linked within participants. The registry does not report the exact statistical model, whether any baseline adjustment was used, or which of the listed time points was treated as the main inferential comparison. The posted outcome is explicitly not reduced to one comparison because it has several categories or time points.

How should uncertainty and significance be read?

In general, a test of statistical significance evaluates how compatible the observed data are with a specified null model, subject to the assumptions of the test. A p-value is not the probability that the treatment is effective, and statistical significance does not by itself describe the magnitude or practical importance of an effect. Effect estimates and confidence intervals are important because they show the scale and precision of the comparison. No primary-outcome p-value, effect estimate, or confidence interval is reported in the registry record. The significance threshold and inferential procedure for the trial are also not reported.

For continuous outcomes, statistical analysis may need to account for the distribution of the observations and how repeated measurements are related. In general, unusual distributions, influential observations, or differences in variability can affect the suitability of a particular model. Repeated measurements from the same participant are not independent in the way measurements from different participants may be; an analysis that uses multiple visits should account for that dependence. These are general considerations, not descriptions of the analysis actually conducted in ACT2, since its detailed statistical methods are not reported in the registry record.

What does the planning illustration mean?

The registry’s sample-size assumptions describe a planning illustration based on the observed effect, rather than the trial’s own design. The illustration assumes a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. It also frames the effect to detect as a stated fraction of the observed effect. Such calculations can illustrate how a hypothetical future study might be sized under specified assumptions. They do not show that the current trial was designed using those assumptions, and they are not observed power.

Sample-size calculations depend on the assumed effect, variability, allocation, and chosen statistical procedure. A planning number is conditional on those assumptions, not a guarantee of precision or a substitute for reporting the actual outcome estimate. The registry record does not report the trial’s own sample-size justification or statistical plan. Without numerical primary-outcome results, the planning illustration cannot be interpreted as evidence about the actual CMT-versus-control effect. It should also not be confused with the number enrolled or with the number of usable observations in a particular analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 5 outcome measures and 5 analyses. The primary reaction-time outcome includes measurements at Study Visit 2 in Week 1, at the Final Visit in Week 2, and change from Visit 2 to the Final Visit. The record notes that the primary outcome has several categories or time points and is not reduced to one comparison. This matters because testing or emphasizing multiple outcomes, visits, or contrasts can increase the chance that at least one result appears notable by chance. In general, a statistical analysis plan may identify a primary contrast or specify methods to address multiple comparisons. Such a plan and any multiplicity adjustment are not reported in the registry record.

The record identifies a technical problem in early collection of the simple hand reaction tests. Once the issue was identified, it was corrected. Measurements collected before correction were considered unreliable and likely inaccurate and were excluded from the analysis. The number of affected participants or observations, the allocation of affected data across groups, and the amount of remaining missing data are not reported in the registry record. The record does not describe an imputation method or sensitivity analysis for missing measurements.

The registry does not report the analysis population, such as whether analyses were based on all randomized participants, participants with usable outcome data, or another defined group. It also does not report a participant flow accounting for exclusions from the primary analysis. These omissions limit assessment of whether the analysis preserved the randomized comparison and how missingness may have influenced the result. No numerical primary-outcome analysis is reported, so the effect of these issues on an estimate cannot be assessed.

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 5% reporting threshold.

The registry’s adverse-event figures record 0 serious adverse events and 0 other adverse events in the CMT group, with 0 deaths. For the wait-list control group, the recorded figures are also 0 serious adverse events, 0 other adverse events, and 0 deaths. The at-risk count is 60 for each group for both serious and other adverse events. No serious adverse-event terms are listed.

These figures describe what is recorded in the registry, not proof that no events occurred outside the scope or collection procedures of the trial. The record does not explain how adverse events were solicited, defined, verified, or monitored, or whether the displayed counts cover the same observation period for every participant. It also does not provide additional detail about event severity or timing. Because the recorded counts are zero in both groups, the registry figures do not provide an observed between-group difference in these event counts. They should be read as registry-reported counts, rather than as a complete assessment of safety or as evidence about risks beyond the study record.

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

The study record establishes that ACT2 was designed to compare chiropractic manipulative therapy with a wait-list control in the SFQ population, including the specified Special Operation Forces subgroup. It identifies dominant-hand simple reaction time as the primary outcome and describes how that task was performed. These details clarify what the investigators intended to measure and the type of comparison the trial was designed to make.

The registry record does not report numerical primary-outcome results. Consequently, it does not show whether mean reaction time was lower or higher in either group, how large a difference was observed, or how uncertain an estimate might be. It also does not establish whether an observed difference was statistically significant or important in practical terms. The trial’s randomized design alone cannot fill in those missing results.

The endpoint concerns response speed on a specific visual-prompt task using the dominant hand. It should not automatically be interpreted as a measure of every aspect of reaction, performance, or function. The registry summary states that the trial also evaluated response times, but the primary endpoint described in detail is simple reaction time. Wider conclusions about unreported outcomes or other settings are not supported by the information in the registry record.

The technical issue in early data collection is relevant to interpretation because affected values were excluded as unreliable. The record does not quantify the affected data or explain how all missing observations were handled. Without that information and without the analysis results, the extent to which available measurements represent the intended trial population cannot be judged. The zero adverse-event counts are likewise limited to the events recorded in the registry and do not establish an absence of risk.

The appropriate statistical reading is therefore descriptive: the record specifies a randomized comparison and an objective reaction-time task, but it does not report the numerical evidence needed to estimate or interpret the primary contrast. No conclusion about treatment benefit or lack of benefit follows from the available registry information.

13. Why This Trial Matters Statistically

This trial is statistically interesting because it links a treatment comparison to a directly timed task rather than relying only on a subjective rating. The primary endpoint has a clear operational description: participants respond to visual prompts with the thumb of the hand identified as dominant, and the average interval from prompt to response is measured in milliseconds. A defined measurement procedure helps readers understand what the endpoint represents and what kind of variation may enter its calculation.

The randomized, parallel design also raises familiar questions about how to compare groups over time. The record names a measurement at Study Visit 2, a measurement at the Final Visit, and change between those visits. Choosing among a visit-specific comparison and a change comparison affects the estimand—the precise quantity the analysis is intended to estimate. The registry does not identify one single primary contrast among these categories, which makes the absence of numerical results particularly consequential.

The data-quality note is another important statistical feature. Early simple reaction-time data were excluded because a technical problem made them unreliable and likely inaccurate. Clear disclosure of such an issue helps readers understand why observations might not contribute to an analysis. At the same time, assessing the consequences requires knowing how much data were affected, how that exclusion related to assignment and follow-up, and how remaining missingness was handled; those details are not reported in the registry record.

Finally, the record illustrates the difference between a completed randomized trial and a complete statistical report. Design information identifies the intended comparison, but interpretation depends on outcome estimates, uncertainty, analysis choices, and missing-data accounting. Those numerical and methodological results are not reported for the primary endpoint. The record therefore serves as a useful description of the research question and measurement approach, while leaving the central treatment-effect estimate unavailable.

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 for statistical interpretation is that numerical primary-outcome results are not reported in the registry record. There are no posted group means, standard deviations, effect estimates, confidence intervals, or significance tests for dominant-hand simple reaction time. The direction, magnitude, and precision of the intended treatment comparison therefore cannot be assessed.

The primary endpoint is associated with several categories or time points, including measurements at Study Visit 2 in Week 1 and the Final Visit in Week 2, as well as change between those visits. The record does not identify a single reduced comparison among these. Without an explicit primary contrast, a reader cannot determine which estimate should carry the main interpretation or how the multiple outcome categories were handled statistically.

The registry notes that data collected before a technical issue was corrected were considered unreliable and likely inaccurate, and were excluded from the analysis. The number of participants or observations affected is not reported. Nor does the record describe the amount or pattern of other missing data, the analysis population, or sensitivity analyses. These omissions prevent a detailed assessment of how data exclusion may have affected the randomized comparison.

Additional design and analysis details are not reported, including the randomization procedure, the identity of the masked role, the treatment schedule, the statistical model, and the trial’s statistical plan or sample-size justification. The registry records adverse-event counts but gives no further account of event collection or observation procedures. These limitations do not establish that the trial was conducted improperly; they identify information unavailable in the registry record and narrow what can responsibly be concluded from it.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Assessment of Chiropractic Treatment Using Reaction and Response Times in Members of the Special Operation Forces (ACT2) — NCT02168153.
• Registry record last updated 2019-04-19; status last verified 2019-01.
• Results first posted 2019-04-19.
• 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

ACT2 (NCT02168153) is recorded as a completed randomized, single-masked, parallel trial sponsored by RAND. Enrollment is listed as 120, with a start date of 2014-08 and a primary completion date of 2016-06. The study compares chiropractic manipulative therapy with a wait-list control in the SFQ population, including Special Operation Forces who are part of the 160th SOAR regiment on flight status.

The primary outcome is mean simple reaction time with the dominant hand, measured in milliseconds, with standard deviation as the dispersion measure. The registry describes measurements at Study Visit 2 in Week 1, at the Final Visit in Week 2, and change from Visit 2 to the Final Visit. It notes that early data affected by a technical problem were excluded as unreliable and likely inaccurate. Numerical primary-outcome results and detailed statistical methods are not reported in the registry record.

For both groups, the registry records 0 serious adverse events, 0 other adverse events, and 0 deaths; the recorded at-risk count is 60 per group for each adverse-event category.