Spectral Dynamics and Speech Understanding by Hearing Impaired People: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Spectral Dynamics and Speech Understanding by Hearing Impaired People (NCT01867515), a non-randomized na study. The primary outcome is Percent Correct Words Identified.

2. Clinical Question

3. Trial Design

This was a completed, non-randomized, single-group study of acoustic distortion of speech. The registry record gives an enrollment of 50 and lists three listener groups: younger normally-hearing listeners, older normally-hearing listeners, and hearing-impaired listeners. The group descriptions specify hearing-threshold and age criteria. The record does not describe random assignment, and its allocation field is non-randomized. Masking is listed as none.

The study was designed to compare speech-identification performance across listener groups and stimulus conditions, not to compare assigned clinical treatments. The experimental conditions included unprocessed stimuli, time-compressed stimuli, time-compressed stimuli expanded in time via gaps, and uncompressed stimuli with portions replaced by silence. Listening tasks took place in quiet and in continuous, speech-shaped background noise. A computational model based on potential information available in speech was also part of the research purpose, but the registry record does not report results from that model.

The primary outcome timeframe describes the average of two blocks per condition, collected over up to three 2-hour visits. Visits were spaced an average of one week apart. The study start is recorded as 2013-08, primary completion as 2016-09, and status as completed. The registry record does not report how participants were allocated to conditions, whether condition order was randomized, or the details of any analysis plan. Although the model field says single group, the record describes comparisons among three listener groups; those groups should not be interpreted as randomized treatment arms.

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

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 Percent Correct Words Identified, measured over average of two blocks per condition obtained over the course of up to three 2-hour visits, spaced an average of one week apart.

The primary endpoint, Percent Correct Words Identified, measures the proportion of words a listener identified correctly in a speech task, expressed as a percentage of words identified. It is an accuracy measure: a higher value would represent more correct word identifications within the condition being assessed, but the registry record does not report endpoint values for any group or condition.

The registry describes the endpoint as a mean and lists dispersion as Full Range. The intended measurement was based on the average of two blocks per condition. Data were collected over up to three 2-hour visits, with visits spaced an average of one week apart. The tasks compared speech stimuli and listening environments, including quiet and continuous, speech-shaped background noise.

This outcome is relevant to the research question because the study aimed to examine speech understanding when acoustic and spectral properties of speech were altered. Percent correct provides an interpretable summary of identification accuracy for each tested condition. It does not, by itself, describe how performance varies from person to person, how much a condition changes performance relative to another, or whether a difference is statistically distinguishable from chance variation. Those conclusions require reported data and an appropriate analysis, neither of which appears in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a non-randomized, single-group study with three listener groups and experimental speech conditions. These labels answer different design questions. Non-randomized means the record does not describe random assignment of participants to the listener groups. Single-group is the registry model classification; it does not erase the fact that the study description compares younger normally-hearing, older normally-hearing, and hearing-impaired listeners. The groups are observational categories rather than randomized treatment arms.

What does percent correct measure?

Percent correct words identified summarizes speech-task accuracy as a percentage. The primary outcome is identified as a mean, with Full Range listed as the dispersion measure. The timeframe specifies an average of two blocks per condition, obtained over up to three 2-hour visits spaced an average of one week apart. The record does not give the actual means or ranges. General explanation: a mean condenses observations into a central summary, while a range describes the spread from the lowest to highest observed values. A mean alone cannot show the full distribution of participant performance.

Why do comparisons need uncertainty estimates?

General explanation: observed group or condition differences can reflect both underlying patterns and sampling variation. A confidence interval is a range of values compatible with the observed data under a specified statistical procedure; it communicates uncertainty around an estimate. A p-value, when used, addresses compatibility between data and a stated null model, not the probability that a hypothesis is true. The registry record reports neither confidence intervals nor p-values for the primary outcome, so the precision and statistical evidence for any contrast cannot be assessed.

What does non-randomized allocation imply?

Because hearing status and age define the listener groups, there is no randomized assignment that makes those groups exchangeable by design. General explanation: randomization can help balance measured and unmeasured baseline characteristics on average, while a non-randomized comparison may reflect differences in group composition as well as the characteristic being studied. Here, the registry record does not report adjusted estimates or enough participant-level information to determine whether such differences were addressed. The observed comparisons, if reported elsewhere, would need to be interpreted as group comparisons rather than automatically as causal effects.

How do repeated conditions affect analysis?

The study description includes multiple stimulus types and listening environments, and the endpoint timeframe refers to blocks per condition. General explanation: measurements from the same person across conditions are often correlated, so analyses may need to account for within-person dependence rather than treating every observation as independent. The record does not report the statistical model, how repeated measurements were handled, or whether condition order was randomized. It also does not report the number of usable observations for each condition.

What is the role of the planning assumptions?

The registry’s sample-size assumptions describe planning illustrations based on an observed effect: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. The record says such calculations are planning illustrations, not the trial’s own design. The study itself is described as non-randomized and includes three listener groups, so a two-arm planning illustration should not be mistaken for the study’s allocation or analysis. General explanation: a sample-size calculation estimates the number of participants needed under chosen assumptions to detect a specified effect with a chosen probability. It does not report the probability that a completed study detected its effect. Such calculations are not observed power.

The registry does not report the sample-size justification for the study itself, the statistical model, covariate adjustment, handling of missing observations, or interim analyses. These omissions prevent a fuller assessment of whether the analysis matched the design and whether uncertainty was appropriately represented. The registry record reports zero analyses, so no statistical procedure or inferential finding for the primary endpoint can be evaluated from this entry.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome measure, but the study description includes several stimulus conditions, two listening environments, and three listener groups. This creates the possibility of multiple condition and group comparisons. The registry record does not report which contrasts were designated as primary beyond naming the primary endpoint, whether additional comparisons were planned, or whether any adjustment for multiple testing was used. It would therefore be unwarranted to assume either that multiplicity was controlled or that it was ignored.

Missing-data methods and analysis populations are not reported in the registry record. The entry does not state how incomplete visits, absent condition measurements, or unusable responses were handled, nor does it give outcome-specific denominators. The enrollment entry alone does not establish how many participants contributed data to every endpoint or condition. No intention-to-treat or per-protocol population is described; those categories may not map naturally onto this non-randomized experimental design.

The record also does not describe the statistical analysis plan, interim analyses, model specification, or adjustment for group characteristics. It lists zero analyses, so no reported analysis can clarify these issues. Without those details, readers cannot assess how missing observations or multiple comparisons may affect the interpretation of any results. These methods are not reported in 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 lists serious adverse events, other adverse events, and deaths separately for the three listener groups. For younger normally-hearing listeners, the at-risk count is 13 for both serious and other events; the reported affected count is 0 for each, and deaths are 0. For older normally-hearing listeners, the at-risk count is 11 for both event categories; the reported affected count is 0 for each, and deaths are 0. For hearing-impaired listeners, the at-risk count is 14 for both event categories; the reported affected count is 0 for each, and deaths are 0.

These entries mean that the registry lists no affected participants for the specified event categories in these groups. They do not establish that every possible adverse experience was systematically measured or that no event occurred outside the registry’s reporting definitions or period. The record does not provide event descriptions, additional detail about collection procedures, or a narrative safety assessment. Because the study involved acoustic distortion tasks rather than a clinical treatment comparison, these counts should be read as registry safety reporting, not as a treatment-effect estimate. The safety entries do not provide evidence about speech-identification performance.

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

The registry entry establishes that investigators studied speech perception in normally-hearing and hearing-impaired listeners using altered speech signals. It identifies the primary measure as percent correct words identified and describes comparisons across listener groups, stimulus types, and quiet or noise conditions. This allows a reader to understand the scientific question and the broad experimental structure.

It does not establish what participants scored, whether one group or condition had higher accuracy, or how large any differences were. No primary-outcome results, inferential analyses, or precision estimates are reported in the registry record. As a result, no conclusion about the direction or magnitude of performance differences can be drawn from this record alone. A completed status is not a substitute for posted findings.

The design also limits what group contrasts could mean. The groups were not randomly assigned, and their definitions are based on age and hearing thresholds. Any contrast among them would be an observed association and could reflect other group differences; the registry record does not report adjusted analyses. Likewise, the description of experimental stimulus conditions does not reveal how condition order or within-person dependence was handled.

The findings, if available in another source, would need to be interpreted in light of the measured task, participant criteria, and listening conditions. The described endpoint concerns correct word identification in the experimental conditions; it is not by itself a measure of everyday communication or a clinical benefit. The record does not report such broader outcomes. The appropriate conclusion from this registry entry is therefore about the study’s aims and methods, not about whether a particular stimulus approach improves speech understanding.

13. Why This Trial Matters Statistically

This study illustrates a statistical distinction between experimental conditions and participant groups. Speech stimuli were altered in several ways, while listeners were classified by age and hearing status. The condition comparisons concern performance under different acoustic inputs; the group comparisons concern participants with different characteristics. Treating these as the same kind of contrast would obscure important differences in design and interpretation.

The non-randomized structure matters because the listener groups were not created by random assignment. Statistical comparisons may describe observed performance differences, but design alone does not make those differences causal. The record’s classification as single group alongside its three described listener groups also shows why registry design labels need to be read together with the detailed study description.

The endpoint is an accessible accuracy measure, but its mean does not reveal the distribution or precision of performance. The registry’s description of repeated blocks and multiple conditions raises questions about within-person correlation and multiplicity. These are general analytic concerns; the registry record does not report how they were handled. The absence of posted endpoint results makes it impossible to assess whether any observed difference was large, precise, or statistically supported.

Finally, the entry separates study completion from evidence reporting. A completed study can still have no results or analysis available in the registry record. Recognizing that distinction helps prevent design descriptions, enrollment information, or safety counts from being mistaken for evidence about the primary research question.

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.

Several limitations follow directly from the registry description. First, allocation was non-randomized and masking is listed as none. Listener groups were defined by age and hearing thresholds, so comparisons across groups cannot be interpreted as randomized contrasts. The registry record does not report adjustment for other participant characteristics or provide enough detail to evaluate potential confounding.

Second, no primary-outcome values or analyses are reported. The registry record therefore does not allow assessment of effect size, precision, statistical significance, or the consistency of performance across conditions. Outcome-specific participant counts and missing-data handling are also not reported. The enrollment entry does not show how complete the endpoint data were for each condition.

Third, the outcome is task-specific: percent correct words identified in experimental speech conditions. The registry record describes quiet and continuous, speech-shaped background noise and several forms of signal alteration, but it does not report broader communication outcomes. Generalization beyond the stated tasks and participant criteria cannot be established from the record.

The record gives age and hearing-threshold criteria for the groups, but does not report further demographic or clinical characteristics. It also does not report condition ordering, the analysis model, multiplicity procedures, or whether repeated observations were accounted for. These missing details limit evaluation of bias and analytic validity. The safety entries are counts, not a comprehensive account of how adverse events were defined or collected. Finally, the registry description includes a computational model as part of the research purpose, but no model results are reported.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Spectral Dynamics and Speech Understanding by Hearing Impaired People — NCT01867515.
• Registry record last updated 2018-04-26; status last verified 2018-04.
• Results first posted 2018-04-26.
• 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

NCT01867515 is a completed, non-randomized, single-group study of speech understanding by younger normally-hearing, older normally-hearing, and hearing-impaired listeners. Its research focus was performance across unprocessed and acoustically altered speech, in quiet and continuous, speech-shaped background noise. The listed intervention is acoustic distortion of speech; the study is not described as a randomized treatment trial.

The primary outcome is Percent Correct Words Identified, measured as a mean and described across blocks and conditions over up to three visits. The registry record lists an enrollment of 50 and reports zero analyses. It does not report primary-outcome values, statistical contrasts, confidence intervals, or p-values. Serious and other adverse-event counts are listed as zero affected participants in each group, with zero deaths. The record identifies the study question and methods but does not provide results that answer the primary question.