Speech Processing in Stuttering: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Speech Processing in Stuttering (NCT04929184), a non-randomized na study. The primary outcome is Phase Locking Value (PLV) - Session 1 Speech Tasks.

2. Clinical Question

In practical terms, the study is designed to characterize speech processing and production during structured tasks. It can describe task performance within the populations and conditions recorded, but the nonrandomized design does not establish that stuttering status caused any observed difference. The endpoint description also does not support a direct adult-versus-child comparison: the instructions differ by age group, and the children’s visit schedule differs from the adults’.

3. Trial Design

NCT04929184, titled “Speech Processing in Stuttering,” is listed as completed. The registry gives a total enrollment of 145 and describes the study as nonrandomized, with no masking and a single-group model designation. It also names four participant groups: adults who stutter, healthy adults, children who stutter, and healthy children. These registry descriptors should be read together: the record includes distinct participant groups, but it does not describe a randomized allocation among comparable treatment arms.

The intervention is behavioral and is called “Speech and non-speech tasks.” The study’s stated purpose is to better understand how people who stutter may process and/or produce speech. Eligible participants completed computer and speech-based tasks during up to two visits. The group descriptions specify two visits for adults who stutter and healthy adults, and one visit for children who stutter and healthy children. The primary endpoint is from Session 1, described as lasting up to 4 hours.

The primary endpoint involves a rhythmic listening-and-whispering task. Adults were not instructed to match the cadence, making their task implicit. Children were instructed to attempt to match it, making theirs explicit. The endpoint therefore represents performance under age-specific instructions rather than one common task applied identically across all groups.

The registry lists the study start as 2022-04-04 and primary completion as 2025-06-16. Its status is completed. The registry record does not report a randomized assignment procedure, a masking procedure, or a treatment protocol, and the study is not described as a trial comparing therapeutic interventions. The record lists three outcome measures, but it does not report analyses for them. The reported sample of 145 is the total enrollment; group-specific enrollment for the primary endpoint is not reported in the registry 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.

Before assignment: 145 participants were enrolled (signed consent form). 26 participants were either lost to follow up (n=15; including 2 participants between Visit 1 and Visit 2) or determined to be ineligible following enrollment (n=11).

Visit 1

Reasons for not completing this period:

Visit 2 (Adults only)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Adults only completed the implicit task on visit 1. Only children completed the explicit task on visit 1 (their only visit).

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 Phase Locking Value (PLV) - Session 1 Speech Tasks, measured over Session 1 (up to 4 hours).

The primary endpoint is mean phase locking value (PLV) for Session 1 speech tasks. Participants heard a series of single syllables spoken rhythmically and whispered “tah” repeatedly while the recording played. PLV measures the degree of synchronization between the participant’s produced speech and the heard speech. The registry describes PLV as a value between 0 and 1: 0 represents a complete mismatch, and 1 represents a perfect match. The specified summary measure is the mean, with standard deviation as the dispersion measure.

Synchronization is used as a measurable way to characterize how speech production relates in time to an external speech signal. A continuous measure can describe variation across participants rather than reducing performance to a simple match-or-no-match classification. The standard deviation describes the spread of individual measurements around the mean, while the mean gives a summary of the group’s measured PLV. These are general interpretations of the statistics, not additional findings from this study.

The endpoint is not identical across the adult and child groups. Adults completed the implicit task and were not told to match the cadence; children completed the explicit task and were told to try to match it. Accordingly, PLV reflects performance under different instructions. The registry does not report the endpoint means or standard deviations, nor does it report a primary outcome analysis. The record therefore gives the measurement definition and task conditions but not an observed estimate of synchronization for any group.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how measurements are summarized, how uncertainty is represented, and what comparisons can reasonably be interpreted. For this study, the registry identifies a continuous primary measure, mean PLV, and standard deviation. It does not provide a statistical analysis plan or report analyses. The explanations below describe general statistical concepts and the implications of the design details that are recorded, not methods confirmed as having been used in this study.

What does a mean PLV represent?

A mean is a summary of the observed values within a group. In this study, the underlying values are PLV measurements, which the registry defines on a scale from 0 to 1, where 0 is a complete mismatch and 1 is a perfect match. The mean condenses a group’s measurements into one central summary. It does not show whether participant values cluster tightly or vary substantially; that requires a measure of spread such as the standard deviation.

The standard deviation describes how dispersed measurements are around the mean. A larger spread indicates more variability among observed measurements, while a smaller spread indicates values more concentrated around the group average. The registry specifies standard deviation as the dispersion measure but does not report its value for any group. Neither a mean nor a standard deviation alone describes the precision of an estimate of the group mean. A confidence interval is commonly used for that purpose: in general, it gives a range of values compatible with the data and the method used to calculate it. No confidence interval is reported for the primary endpoint.

Why do task instructions matter?

Adults and children did not perform the same instructed task. Adults completed an implicit task without instructions to match cadence; children completed an explicit task with instructions to try to match it. This distinction affects the interpretation of PLV: the measure is tied not only to participant characteristics but also to the task condition. A contrast across these groups would therefore not isolate an age-related difference or a stuttering-related difference. The registry does not report a model that accounts for the differing instructions.

More generally, a statistical comparison is most interpretable when it compares groups measured under comparable conditions. Here, the record itself cautions that the nonrandomized arms are not a like-for-like control comparison. Nonrandomized group differences can reflect differences between participants or study conditions as well as the characteristic being studied. Randomization can help balance measured and unmeasured factors on average, but this study is not listed as randomized. The registry does not report methods for adjusting group comparisons or controlling confounding.

What does nonrandomized mean for inference?

In a randomized study, assignment to conditions is determined by a chance process. In a nonrandomized study, the record does not indicate that groups were created through such assignment. Comparisons can still describe observed measurements, but causal conclusions require assumptions and supporting methods that are not reported. In this study, the groups are defined by stuttering status and age category, while task instructions also differ. The design can support descriptive characterization of task performance if results are reported, but the registry’s design information alone does not establish that group membership caused an outcome difference.

The “single group” model label appears alongside the four named participant groups. That combination does not supply a detailed analysis specification. The registry record does not explain how the model designation relates to the group comparisons, whether repeated observations were modeled, or whether a particular statistical test was planned. These details should not be inferred from the endpoint type or study title.

What can planning calculations tell readers?

Sample-size planning uses assumptions about the effect to detect, the variability of measurements, the allocation between groups, and the chosen statistical method. The general purpose is to estimate the number of participants needed under those assumptions; a planning estimate is not an observed result and is not “observed power.” The registry’s planning description specifies a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the target effect is a fraction of the observed effect. Those are planning assumptions, not evidence that the study used this approach to design enrollment.

The registry does not report a sample-size justification for the study’s own design. It also does not provide the observed effect or variability needed to interpret planning illustrations for this endpoint. Without reported group results, an illustration based on an observed effect cannot be evaluated as a measure of how much evidence the study found. The total enrollment of 145 does not by itself establish whether the study had adequate precision for a particular group estimate or comparison.

What information is missing for a full statistical assessment?

A full assessment would ordinarily require the outcome estimates, group-specific sample sizes, uncertainty intervals, and a clear account of the analysis population. For a task involving recorded speech, details about usable measurements and exclusions would also help explain which observations contribute to the endpoint. The registry record does not report those items. It lists three outcome measures and zero analyses, so the record supplies outcome definitions but not reported statistical findings. No particular hypothesis test, covariate adjustment, missing-data method, or interim analysis is reported in the registry record.

These omissions do not establish that the study lacked such procedures; they mean those procedures cannot be described from the registry record. Statistical interpretation should therefore remain at the level of design and measurement: the study was intended to assess speech synchronization through PLV under specified task conditions, but the posted record does not show the estimates or analyses needed to judge the magnitude or precision of any observed pattern.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures and identifies mean PLV for Session 1 speech tasks as the primary endpoint. It also names R Statistic (Resultant Vector Length) as a secondary outcome. The record does not report analyses for these outcomes, and it does not describe how multiple outcomes or multiple group comparisons were handled. In general, testing many outcomes or contrasts can increase the chance that at least one result appears notable by chance. Methods such as prespecifying a primary comparison or adjusting for multiple testing can address that issue, but no such procedure is reported in the registry record.

The other outcome measure descriptions and their analysis details are not reported in the registry record. The record does not state which comparisons were planned, whether subgroup analyses were intended, or how multiplicity was addressed. No interim analysis plan is reported in the registry record. These details should not be inferred from the existence of outcome measures.

Missing-data methods are also not reported. The total enrollment is 145, but the record does not give group-specific numbers contributing to PLV, identify unusable recordings, describe missing observations, or state how missing data were handled. The analysis populations—such as whether all enrolled participants or only those with evaluable recordings were included—are not reported in the registry record. The endpoint is specified for Session 1, and the group descriptions indicate different visit schedules, but the record does not describe whether incomplete visits affected the primary analysis.

These gaps limit interpretation of both the results and their precision. Without an analysis population and missing-data account, readers cannot establish how the endpoint summaries relate to enrollment. Without a multiplicity plan, the statistical meaning of any reported exploratory comparisons would be difficult to assess. The registry provides no outcome analyses with which to make those evaluations.

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 adverse-event record lists four groups: adults who stutter, healthy adults, children who stutter, and healthy children. For each group, the registry reports zero serious adverse events, zero other adverse events, and zero deaths. The numbers listed as at risk are 55 for adults who stutter, 67 for healthy adults, 13 for children who stutter, and 10 for healthy children. These figures describe the safety entries in the registry; they do not provide the PLV analysis sample sizes.

Zero recorded events means that the registry reports no events in the stated categories among the participants listed as at risk. It is not equivalent to proof that no event could occur, nor does it describe how events were solicited, defined, or reviewed. The record does not provide event narratives, follow-up details, or additional information about safety monitoring. No serious adverse-event terms are listed.

The study involved behavioral speech and non-speech tasks rather than a treatment comparison. The adverse-event entries should therefore be read as registry safety reporting for the study groups, not as a comparison of harms between interventions. Because no events are recorded, the registry does not offer estimates of differences in event risk across groups. The reported zeros are descriptive entries and should not be interpreted as evidence about safety beyond the recorded participants and categories.

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

This study’s registry record describes a way to measure synchronization between a person’s whispered speech and rhythmic speech heard in a recording. PLV is defined on a scale from 0 to 1, with the endpoints corresponding to complete mismatch and perfect match. The record identifies the intended summary as the mean and the dispersion measure as standard deviation. It also states that adults completed an implicit task and children an explicit task.

Those details clarify what the primary endpoint is intended to capture, but they do not show the observed PLV values. The registry record does not report the group means, standard deviations, confidence intervals, or analyses. Therefore, it cannot establish the magnitude or direction of any group pattern, how precisely an estimate was measured, or whether a statistical comparison supports a difference. An endpoint description is not a result.

The design also sets limits on what group comparisons could mean. Allocation is listed as nonrandomized, and the record cautions that the arms are not a like-for-like control comparison. In addition, the adult and child tasks use different instructions. If numerical contrasts were available, they would need to be interpreted in light of these design and task differences; they would not, by themselves, show that stuttering status caused a difference in synchronization.

The record does not establish whether the task measure captures speech processing or production outside the specific recorded task, or whether it predicts outcomes beyond the study. The study’s stated aim is to better understand how people who stutter may process and/or produce speech. Its endpoint is one operational measure within that aim. The registry does not report results that would determine how well the measure addresses the broader question.

In short, the study record identifies the participants, task conditions, and endpoint, and records no adverse events in the listed categories. It does not provide the primary outcome findings needed to characterize synchronization in the groups. Readers should distinguish information about what was measured from evidence about what the measurements showed.

13. Why This Trial Matters Statistically

This study illustrates an important statistical distinction between defining a measurable endpoint and reporting evidence from that endpoint. PLV gives a specific way to quantify synchronization between produced and heard speech during a structured task. The registry further identifies the planned summary and dispersion measure. These choices make the measurement concept interpretable, but without results, readers cannot assess its observed distribution or precision.

It also highlights how task conditions shape the meaning of a comparison. Adults completed an implicit task, while children completed an explicit task. The same named endpoint can reflect different behavioral demands when instructions differ. Statistical interpretation must account for that design feature rather than treating every group contrast as if it arose from identical conditions.

The nonrandomized design is another reason to separate description from causal inference. Group-level measurements can be useful for characterizing performance, but a contrast between groups does not establish that group membership caused the contrast. The registry explicitly cautions that the arms are not a like-for-like control comparison. This is relevant when interpreting studies that include healthy comparison groups alongside participant groups defined by a condition.

Finally, the record demonstrates why outcome values and analysis details are essential to evaluating a study. Enrollment, endpoint definitions, and completed status cannot replace the estimates, uncertainty measures, analysis populations, and missing-data information needed to assess findings. The registry lists outcome measures but no analyses. That absence leaves the central statistical question unresolved in the posted record: the extent and precision of synchronization measured by PLV across the specified groups and tasks.

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 primary limitation for interpreting this study is that the registry record does not report the primary PLV results or any analyses. Group means, standard deviations, confidence intervals, and group-specific endpoint sample sizes are not reported in the registry record. As a result, neither the observed pattern nor its precision can be assessed from the posted results.

The study is listed as nonrandomized, and the registry cautions that the groups are not a like-for-like control comparison. The adult and child populations also performed different task conditions: adults were not instructed to match the cadence, while children were instructed to try to match it. These features complicate direct comparisons across groups and limit causal interpretation.

The overall enrollment is 145, but enrollment by group for the primary endpoint is not reported in the registry record. The record does not describe exclusions, usable speech recordings, missing observations, or the analysis population. Group visit schedules differ, with adults described as attending two visits and children one visit; the registry does not explain how those schedules affect outcome availability.

The record lists three outcome measures but does not report the analyses, the statistical plan, or how multiple outcomes and comparisons were handled. It also does not report a sample-size justification for the study’s own design. These omissions mean that readers cannot evaluate the statistical procedures, missing-data assumptions, or multiplicity implications. They should be understood as limits of what the registry record documents, not as evidence that a particular method was or was not used.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Speech Processing in Stuttering — NCT04929184.
• Registry record last updated 2026-07-16; status last verified 2026-07.
• Results first posted 2026-07-16.
• 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

NCT04929184, “Speech Processing in Stuttering,” is listed as completed, with enrollment of 145. The registry describes a nonrandomized study with no masking and a single-group model designation. Its behavioral activities are speech and non-speech tasks involving adults and children who stutter and healthy comparison groups. Adult groups are described as having two visits; child groups as having one visit.

The primary outcome is mean PLV for Session 1 speech tasks, with standard deviation as the dispersion measure. Adults completed an implicit task; children completed an explicit task. PLV is defined as a measure of synchronization between whispered and heard speech, ranging from 0 for complete mismatch to 1 for perfect match. The registry lists three outcome measures and names R Statistic (Resultant Vector Length) as secondary, but reports zero analyses. Primary outcome values and their uncertainty are not reported in the registry record.

The adverse-event entries report zero serious events, zero other events, and zero deaths in each of the four named groups. The record lists the study as completed, but the endpoint results needed to assess the primary statistical question are not included.