Validation of the Drug Impaired Driving Scenario (DIDS) on the CRCDS-miniSim: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Validation of the Drug Impaired Driving Scenario (DIDS) on the CRCDS-miniSim (NCT04970342), a randomized phase 1 study. The primary outcome is Standard Deviation of Lateral Position (SDLP).

2. Clinical Question

The primary outcome is standard deviation of lateral position (SDLP), measured in centimeters. The record describes it as a measure of the ability to keep the vehicle straight in the lane during a rural drive with a concurrent divided-attention task. Measurement was specified over one hour during the simulator drive conducted 45 minutes post-dose at Treatment Visits 1, 2, and 3.

The question is about whether this simulator scenario can register acute changes under the study conditions, not about real-world driving outcomes. The registry does not report results on actual driving, and the posted summaries alone do not establish whether an observed difference is statistically reliable or attributable to treatment.

3. Trial Design

The registry classifies this as a randomized, triple-masked, crossover Phase 1 study. Its status is completed. The listed study start date is 2021-07-16, and primary completion is listed as 2021-08-21. Enrollment is 13. The brief description says subjects took part in a four-visit protocol at the National Advanced Driving Simulator, part of the University of Iowa.

The protocol description includes questionnaires, computerized cognitive tasks, and simulator driving. Treatments included a lactose placebo capsule or 0.75 mg alprazolam, and active vaporized cannabis or placebo cannabis. The active cannabis is described as 500 mg with 6.18% THC and less than 0.025% CBD; placebo cannabis is described as 0% THC and 0% CBD. The three posted outcome groups are double placebo, active alprazolam with placebo cannabis, and placebo alprazolam with active cannabis.

In a crossover study, participants receive more than one treatment condition over the course of a study; the design can allow comparisons that account for measurements from the same participant. That is a general description of crossover designs, not a complete account of this study’s implementation. The treatment sequence, allocation procedure, and any washout interval are not reported in the registry record. The registry labels masking as triple but does not specify which roles were masked or how masking was maintained.

For SDLP, the record lists a mean and standard deviation for each posted group. Each group summary lists 8 participants. These group summaries should not be added together or treated as independent groups without further information, particularly because the design is identified as crossover. The record does not report the number of observations contributing to each visit-specific measurement or explain how repeated observations were handled.

The study’s stated objective was to assess the acute effects of cannabis relative to placebo on simulated driving and to use alprazolam as an active comparator for assay sensitivity. The record does not report a statistical analysis plan, planned contrasts, or a sample-size justification.

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.

Before assignment: Of the 13 subjects enrolled, 8 were randomized to one of six sequences counterbalancing the three treatment arms. Subjects were randomized at intake for Treatment Visit 1. Of the 5 subjects enrolled but not randomized, 3 did not meet study criteria at the screening visit, 1 had scheduling conflicts, and 1 failed to show for Treatment Visit 1. There was a minimum 7-day washout between the Screening Visit and intake for Treatment Visit 1. All randomized subjects completed all treatment arms.

Treatment Visit 1 (1 Day)

Washout (7 Days)

Treatment Visit 2 (1 Day)

Washout (7 Days)

Analysis population for the primary outcome, as defined in the registry: All Subjects

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.

Population: All subjects randomized completed all study arms/treatments, but in a different randomization sequence. Data was not used from subjects enrolled but not randomized.

6. Primary Endpoint

The registry lists the primary outcome as Standard Deviation of Lateral Position (SDLP), measured over over one hour during the course of the simulator drive conducted 45 minutes post-dose at Treatment Visit 1, 2, and 3.

The primary endpoint is standard deviation of lateral position, or SDLP, reported in centimeters as a mean with a standard deviation. The registry describes SDLP as reflecting the ability to keep the vehicle straight in the lane. It was collected during a rural simulator drive that included a concurrent divided-attention task. The specified measurement window was one hour during a drive conducted 45 minutes after dosing at Treatment Visits 1, 2, and 3.

SDLP is a continuous measure: larger values represent more variability in lateral position during the drive. This general interpretation explains the direction of the measure; it does not by itself establish a clinically important threshold or a treatment effect. The registry does not report a threshold for interpreting an individual value or a meaningful between-condition change.

A simulator endpoint can be useful for evaluating performance under controlled driving conditions, where the task and measurement context can be specified. In this study, the divided-attention task is part of that context, so the result pertains to performance in the described simulator scenario rather than every driving situation. The registry does not report validation criteria beyond the stated objective of evaluating sensitivity to cannabis effects and the planned use of alprazolam to demonstrate assay sensitivity.

The reported group means are 25.49 cm for double placebo, 37.85 cm for active alprazolam with placebo cannabis, and 33.09 cm for placebo alprazolam with active cannabis. Their corresponding standard deviations are 5.737, 6.434, and 12.38. These are descriptive summaries; without reported treatment contrasts and uncertainty estimates, they do not establish the size or statistical reliability of a treatment effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry consists of descriptive summaries for the primary continuous endpoint and safety counts. No analyses are posted. The registry reports the endpoint as a mean and standard deviation, but does not provide a treatment-effect estimate, confidence interval, p-value, or model specification. The distinction matters: a displayed group mean describes the observed data, while an inferential comparison estimates how the outcomes differ between treatment conditions and quantifies uncertainty around that comparison.

What does the mean describe?

For a continuous outcome such as SDLP, the mean is a measure of the center of the observed values. The posted means are 25.49 cm for double placebo, 37.85 cm for active alprazolam with placebo cannabis, and 33.09 cm for placebo alprazolam with active cannabis. These summaries do not indicate how each participant’s outcome changed between conditions. In a crossover study, that within-participant pattern may be important, because the same participant can contribute observations under different treatment conditions.

What does the standard deviation describe?

The standard deviation describes the spread of observations around a mean. The posted values are 5.737, 6.434, and 12.38 for the double-placebo, active-alprazolam, and active-cannabis groups, respectively. It is not the same as a confidence interval or the standard error of a mean. A larger standard deviation indicates more observed variation in the data summarized, but does not reveal why that variation occurred. The registry does not specify whether the spread is calculated over participant-level summaries, visit-level measurements, or another unit of analysis.

General statistical context: a confidence interval expresses uncertainty around an estimate, under the assumptions of the method used to calculate it. Its width depends on factors such as the amount of information and variability in the data. No confidence intervals are reported for these outcomes, so the precision of treatment comparisons cannot be assessed from the listed means and standard deviations alone.

Why does the crossover design matter?

In general, crossover data include observations that may be paired within participants. Outcomes from the same person can be correlated across treatment conditions. An analysis that accounts for this correlation can use information from within-person changes; an analysis that ignores it may misstate uncertainty. The registry identifies the model as crossover but does not report treatment sequences, period effects, washout details, or the statistical method used to account for repeated observations. Consequently, the posted arm-level summaries are not enough to reconstruct an appropriate crossover analysis.

General statistical context: repeated measurements can also vary with time or visit. An analysis may need to distinguish treatment effects from period or sequence effects, depending on the design and the prespecified analysis. The record does not report whether such effects were assessed or how they were handled. No assumptions about those methods can be made from the design label alone.

What can be concluded without a reported test?

The numerical ordering of group means is descriptive. It is not a test of a treatment effect. A p-value, when reported, addresses compatibility between data and a specified null model under the analysis assumptions; it does not quantify the probability that a treatment works. A confidence interval would provide information about the range of effects compatible with the data and method. Neither type of inferential result is reported for SDLP. The registry also does not state a clinically meaningful threshold for SDLP, so the practical importance of a difference cannot be assessed from these summaries.

The study objective says that assay sensitivity would be demonstrated by a significant effect of 0.75 mg alprazolam on driving and cognitive endpoints. That is a statement of intent, not a reported finding. The record does not give a significance test or analysis result for alprazolam. The same distinction applies to the primary objective of evaluating cannabis relative to placebo.

What do the planning assumptions mean?

The registry’s sample-size assumptions describe a planning illustration based on an observed effect, rather than the trial’s own design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and detection of a stated fraction of the observed effect. Such illustrations are planning calculations: they ask how many participants per arm would be needed for a specified power under the assumptions used. They are not observed power, and they do not show the probability that the completed study detected an effect. The record does not report the trial’s sample-size justification or provide the analysis details needed to treat a planning illustration as a prespecified design calculation.

General statistical context: planning estimates depend on assumptions about the effect to detect, variability, allocation, and analysis. If the assumed effect is based on an observed estimate, it may be unstable, especially when the underlying study is small. Calculated sample sizes should therefore be read as conditional illustrations, not as evidence about the reliability of the observed treatment effect. The registry does not report an inferential treatment estimate or its uncertainty for SDLP, so the planning assumptions do not substitute for a treatment-effect analysis.

Finally, the registry lists two outcome measures, including Lane Exceedences as a secondary outcome, but does not report analyses. Without the planned analysis and any adjustment strategy, it is not possible to assess how multiple outcomes or comparisons were handled. The descriptive SDLP summaries remain useful for understanding what was posted, but they cannot answer those inferential questions on their own.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("'Sober' or Double Placebo", "Active Alprazolam (Xanax), Placebo Cannabis", "Placebo Alprazolam (Xanax), Active Cannabis")
n   <- c(8, 8, 8)
m   <- c(25.49, 37.849, 33.086)
sp  <- c(5.737, 6.434, 12.375)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  'Sober' or Double Placebo  8  25.490  5.737  20.694  30.286
CARM  Active Alprazolam (Xanax), Placebo Cannabis  8  37.849  6.434  32.470  43.228
CARM  Placebo Alprazolam (Xanax), Active Cannabis  8  33.086  12.375  22.740  43.432

11. Multiplicity, Missing Data and Analysis Populations

The registry lists SDLP as the primary outcome and Lane Exceedences as a secondary outcome. It records two outcome measures and zero analyses. No multiplicity procedure, hierarchy of secondary outcomes, or adjustment for multiple comparisons is reported in the registry record. This means the available information does not show how the study planned to control the chance of false-positive findings across outcomes or treatment contrasts.

Missing-data handling is also not reported. The primary outcome population is labeled all subjects, but the record does not explain whether all enrolled participants contributed data, how incomplete visits were treated, or whether any imputation was used. Enrollment is listed as 13, while the outcome summaries list 8 participants for each posted treatment group. Because the study is identified as crossover, those group counts should not be interpreted as separate participant groups or combined; the registry does not report a flow diagram or analysis-level accounting that clarifies the relationship.

The record does not specify the statistical model, treatment contrasts, assumptions about missing observations, or handling of repeated measurements. It also does not report whether analyses followed intention-to-treat, per-protocol, or another population definition. The field identifying the primary population as all subjects is not enough to determine which observations entered a particular analysis. These gaps limit assessment of bias, precision, and the relevance of the posted summaries to the planned objectives.

12. 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.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for the three posted treatment groups. The serious adverse events affected count is 0 among 8 at risk in each group: double placebo, active alprazolam with placebo cannabis, and placebo alprazolam with active cannabis. Deaths are listed as 0 for each group. These are the posted counts; they do not establish that no unrecorded events occurred or that risks are equivalent between conditions.

For other adverse events, the affected count is 1 among 8 at risk in the double-placebo group, 0 among 8 in the active-alprazolam group, and 0 among 8 in the active-cannabis group. The registry does not provide a term for the non-serious event in the available summary. The serious adverse event terms list is empty.

These counts are descriptive and arise from a small study. A zero count does not mean that an event is impossible, and counts alone do not quantify comparative safety. The record does not report severity details beyond the serious-versus-other categories, event timing, or a statistical comparison of adverse events. The group summaries should be understood as recorded safety counts, not as a basis for medical advice or a broad safety conclusion.

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

The posted results show the SDLP means and standard deviations recorded for three treatment groups in a simulator study. They provide a descriptive view of lane-position variability during a rural drive with a concurrent divided-attention task. The group means are 25.49 cm for double placebo, 37.85 cm for active alprazolam with placebo cannabis, and 33.09 cm for active cannabis with placebo alprazolam. The associated standard deviations are 5.737, 6.434, and 12.38.

Those summaries do not establish the treatment effect of cannabis or alprazolam. The registry does not report a statistical contrast, confidence interval, or p-value for SDLP. It also does not report how repeated observations from the crossover design were analyzed. Without those details, the uncertainty around a comparison and the strength of evidence for a treatment-related change cannot be assessed.

The stated objective includes validating the Drug Impaired Driving Scenario and demonstrating assay sensitivity through an alprazolam effect. The posted record does not include inferential results that confirm either objective. The values should not be treated as proof that the simulator did or did not detect a drug effect.

The endpoint is a simulator measure under specified conditions. It is not a direct measure of real-world driving behavior, and the registry does not report outcomes from on-road driving. Nor does the record provide a threshold that would translate an SDLP value into a meaningful safety judgment. The study’s adverse-event counts are also descriptive and do not provide a comparative safety analysis.

Planning illustrations based on an observed effect, if used, should be interpreted as conditional sample-size calculations rather than observed power or evidence of efficacy. The registry’s stated planning assumptions do not replace a reported statistical analysis of the completed study. Overall, the available results describe the posted observations but leave important questions about precision, analysis, and generalizability unresolved.

14. Why This Trial Matters Statistically

This study raises a statistical measurement question: can a specified simulator scenario register performance changes under controlled drug and placebo conditions? That question differs from asking whether a treatment changes real-world driving outcomes. A simulator endpoint can be studied under a defined task and measurement window, and SDLP provides a continuous measure of lateral-position variability during that task.

The crossover designation is statistically important because observations may be related within participants. Properly accounting for that dependence can affect both the estimated treatment contrast and its uncertainty. The registry provides group-level means and standard deviations but does not report the model or within-participant comparisons. This illustrates why descriptive summaries alone may be insufficient for interpreting a crossover trial.

The registry also makes clear that an active comparator can serve a methodological purpose: the stated objective uses alprazolam to assess assay sensitivity. But a planned positive-control role is not the same as evidence that the expected effect was observed. That conclusion requires reported analyses, which are not included in the registry record.

Finally, the study highlights the difference between planning and inference. Sample-size planning assumptions can illustrate the information required for a target analysis, but they do not indicate the power actually achieved or validate the observed result. For clinical researchers, the record underscores the importance of reporting treatment contrasts, uncertainty, analysis populations, missing-data methods, and handling of repeated measures alongside descriptive outcome summaries.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

Several trial-specific details needed to interpret the SDLP summaries are not reported in the registry record. Although the study is labeled randomized, triple-masked, and crossover, the record does not describe the randomization procedure, the masked roles, the treatment sequence, or any washout interval. It also does not give the statistical model or explain how repeated measurements across treatment visits were handled.

The primary outcome population is listed as all subjects, but the registry does not provide participant flow or explain the relationship between enrollment of 13 and the outcome summaries that each list 8. It does not specify how missing observations, incomplete visits, protocol deviations, or analysis exclusions were handled. The measurement timeframe refers to Treatment Visits 1, 2, and 3, while the study description says the protocol involved four visits; the role of the additional visit is not explained in the outcome description.

For SDLP, only group means and standard deviations are posted. No treatment contrasts, confidence intervals, p-values, or model estimates are reported, so comparative precision and statistical evidence cannot be evaluated. No threshold for a meaningful SDLP difference is reported. The registry lists Lane Exceedences as a secondary outcome but does not post analyses for it.

The record’s title refers to CRCDS-miniSim, while the brief objective refers to the CRCDS-2 driving simulator. The registry does not explain this naming difference. Finally, the results concern a simulator task under the specified study conditions. The record does not report real-world driving outcomes, so external relevance beyond that task cannot be assessed from these results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Validation of the Drug Impaired Driving Scenario (DIDS) on the CRCDS-miniSim — NCT04970342.
• Registry record last updated 2023-07-25; status last verified 2022-08.
• Results first posted 2023-07-25.
• 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.

19. Record Summary

The completed Phase 1 study is listed as randomized, triple-masked, and crossover, with enrollment of 13. Its stated objective was to evaluate whether the Drug Impaired Driving Scenario could detect acute cannabis effects on simulated driving, with alprazolam as an active comparator for assay sensitivity. The protocol description includes a four-visit study at the National Advanced Driving Simulator, part of the University of Iowa.

The primary outcome is SDLP in centimeters, measured during a rural simulator drive with a divided-attention task. The registry posts means and standard deviations for double placebo, active alprazolam with placebo cannabis, and active cannabis with placebo alprazolam. It also lists Lane Exceedences as a secondary outcome. No statistical analyses are reported. The record does not provide treatment contrasts, uncertainty estimates, a missing-data approach, or a statistical model for the crossover data.