This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Investigations of Ear Tip Performance, Perceptions, and Experiences (NCT05725824), a randomized na study. The primary outcome is Real Ear Measures.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT05725824 |
| Phase | NA |
| Condition | Hearing Aids |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | None (open label) |
| Enrollment | 30 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Arizona |
| Results posted | Yes |
2. Clinical Question
Population
The study enrolled 30 participants described as having normal hearing. The hearing aids were programmed to simulate a mild, flat, sensorineural hearing loss of 30 dB HL from 250-8000Hz. Further eligibility criteria and participant characteristics are not reported in the registry record.
Intervention
The study compared custom earmolds made in-house using resin and PLA with a third-party control earmold. The in-house process involved scanning and editing custom earmold impressions, then fabricating the earmolds with different 3D-printing approaches.
Comparator
The comparator was an acrylic earmold made by a professional third-party manufacturer from ear canal impressions. The registry describes the control as the reference for comparison with the in-house study earmolds. Further details about the control earmolds are not reported in the registry record.
Primary question
The primary question was whether real-ear acoustic measurements differed when participants wore the different earmold types with a hearing aid. A thin microphone tube measured sound in the ear canal while participants sat in front of a speaker playing sound samples. Measurements were recorded across frequencies from 250-8000Hz. The study also described subjective ratings of sound quality and physical comfort, but the primary endpoint listed in the registry record is Real Ear Measures. Numerical estimates for the comparison are not reported in the registry record, so the direction and size of any differences cannot be described.
3. Trial Design
This was a randomized, unmasked, crossover study of a device intervention. Enrollment was 30, and the study status is completed. The registry lists the start date as 2023-07-30 and the primary completion date as 2024-01-17. The sponsor was the University of Arizona.
Each participant was evaluated while wearing a hearing aid with different earmold types. The three types were a third-party control made in acrylic, an in-house resin earmold, and an in-house PLA earmold. The registry describes custom impressions being scanned and edited before the in-house earmolds were fabricated. The intervention is listed as a BTE hearing aid with compatible earmolds.
The registry lists three sequences: third-party control followed by in-house PLA and then in-house resin; in-house resin followed by third-party control and then in-house PLA; and in-house PLA followed by in-house resin and then third-party control. This is consistent with a design in which the order of earmold conditions varies. The registry does not report further details about how random assignment to sequence was conducted, whether order was balanced, or whether participants or assessors were blinded. Masking is listed as none.
Because the same participants underwent measurements with multiple earmold types, the comparisons are within-participant rather than comparisons of separate treatment groups. The registry describes repeated-measures analysis of variance, followed by paired t-tests with Bonferroni correction for comparisons between earmold materials. Further details about the statistical model, such as its treatment of period or sequence effects, are 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.
Overall Study
| Stage | 3rd Party Control, Then In-house PLA, Then In-house_RES | In-house_RES, Then 3rd Party Control, Then In-house PLA | In-house PLA, Then In-house_RES, Then 3rd Party Control |
|---|---|---|---|
| STARTED | 10 | 10 | 10 |
| COMPLETED | 10 | 10 | 10 |
| NOT COMPLETED | 0 | 0 | 0 |
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.
| Characteristic | Unit | Overall Group |
|---|---|---|
| Participants analysed | 30 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 30 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 24 |
| Sex: Female, Male: Male | Participants | 6 |
| Race/Ethnicity, Customized: American Indian or Alaska Native | Participants | 1 |
| Race/Ethnicity, Customized: Asian | Participants | 2 |
| Race/Ethnicity, Customized: Black or African American | Participants | 2 |
| Race/Ethnicity, Customized: Hispanic/Latino | Participants | 7 |
| Race/Ethnicity, Customized: White/Non-hispanic | Participants | 14 |
| Race/Ethnicity, Customized: More than one race | Participants | 4 |
6. Primary Endpoint
The registry lists the primary outcome as Real Ear Measures, measured over 15 minutes.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | dB SPL |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is Real Ear Measures, reported as a mean with standard deviation in dB SPL. It describes acoustic measurements in the ear canal while a participant wears a hearing aid and one of the earmold types. A thin microphone tube is placed in the ear canal, and sound is played from a speaker while the participant sits in front of it. The registry says measurements are recorded across frequencies from 250-8000Hz. The listed timeframe is 15 minutes.
As a general measurement concept, real-ear measurements characterize the sound reaching the ear with the hearing aid and earmold in place. Measuring in the ear canal allows the study to assess acoustic performance under the tested fitting conditions, rather than relying only on a device setting or a participant’s impression. Mean values describe the average measurement, while standard deviations describe variation around that average. Neither quantity alone establishes whether differences between earmold types are statistically distinguishable or practically important.
The registry describes repeating the measurement after changing the earmold type for each participant. It also says the analysis compared earmold types across frequencies. Numerical means, standard deviations, and between-type estimates are not reported in the registry record, so the size and precision of the observed acoustic differences cannot be characterized.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a repeated-measures comparison of real-ear acoustic measurements across three earmold types. Since participants were measured under more than one condition, the main comparison is within participant: each participant’s measurements under one earmold type can be compared with that same participant’s measurements under another type. This approach can account for stable differences between participants, such as differences in ear anatomy, when the analysis is specified and conducted appropriately.
However, the registry record does not report numerical primary-outcome results. Means, standard deviations, pairwise differences, confidence intervals, and p-values are not reported in the registry record. Without those estimates, it is not possible to state which earmold type had higher or lower measurements, how large any contrast was, or how precisely it was estimated. The study’s completion status and enrollment count do not substitute for outcome results.
The endpoint description notes that measurements were collected across a range of frequencies. That means results may vary by frequency, and an overall statement about acoustic performance could conceal frequency-specific patterns. The registry notes that the groups were collapsed for repeated-measures analysis of variance and that post-hoc paired t-tests with Bonferroni correction were used to compare material types. The exact outcome summaries, comparisons, and frequency-specific findings are not reported in the registry record.
For general interpretation, a confidence interval describes a range of values compatible with the data under the analysis assumptions. Its width helps convey precision, while a p-value addresses compatibility with a specified null hypothesis under a statistical model. Neither measure alone indicates whether a difference matters in practice. The registry record does not report confidence intervals or p-values for the primary endpoint, nor does it define a threshold for an important acoustic difference.
The randomized crossover structure is useful for comparing conditions within participants, but it also makes order and period considerations relevant. The registry lists different earmold sequences, but does not report whether the analysis adjusted for sequence, period, or carryover. It also does not report enough information to assess missing measurements or whether all enrolled participants contributed data to each comparison. Therefore, interpretation must remain limited to the design and methods described, not a claim about the direction or magnitude of any result.
9. Statistical Methods Explained
The registry describes repeated measurements from the same participants under different earmold conditions. The statistical methods named are repeated-measures analysis of variance and post-hoc paired t-tests with Bonferroni correction. The registry record does not provide the numerical results or a complete statistical analysis plan. The explanations below are general descriptions of these methods, not additional claims about how every modeling decision was handled in this study.
Why use a repeated-measures analysis?
In a repeated-measures design, each participant contributes measurements under multiple conditions. Measurements from the same person are usually related: a participant with relatively high measurements under one condition may also have relatively high measurements under another. A repeated-measures analysis accounts for this dependence instead of treating all measurements as if they came from unrelated people.
This can be an efficient way to compare conditions because stable differences between participants are separated from changes within participants. The interpretation still depends on the analysis assumptions and on how the repeated observations are represented. The registry identifies repeated-measures analysis of variance, but details such as the model specification, covariance assumptions, treatment of incomplete observations, and any adjustments for sequence or period are not reported in the registry record.
What does analysis of variance test?
In general, analysis of variance evaluates whether average responses differ across conditions, relative to the variability in the data. In a repeated-measures version, the method recognizes that observations from one participant belong together. The registry says that groups were collapsed for the repeated-measures comparison of earmold types. It does not report the test statistic, degrees of freedom, p-value, or a numerical estimate of the overall condition effect.
When an overall test includes multiple conditions, it does not by itself identify which particular pairs differ. Follow-up comparisons can examine specific pairs, but repeated testing creates a multiplicity issue: the more comparisons made, the greater the chance of at least one false-positive finding if each test is interpreted independently at the same threshold.
Why paired t-tests?
A paired t-test compares two conditions using within-participant differences. For each participant with measurements under both conditions, the analysis considers the difference between that participant’s two measurements. The test evaluates whether the average of those paired differences is distinguishable from zero under its assumptions. The registry states that paired t-tests were used after the repeated-measures analysis to compare earmold material types. The paired estimates and test results are not reported in the registry record.
What does Bonferroni correction do?
As a general method, Bonferroni correction adjusts for multiple comparisons by using a more stringent criterion for each test, or by adjusting the reported p-values. This helps control the probability of false-positive conclusions across a defined family of tests. Its interpretation depends on which comparisons are included in that family. The registry reports that a Bonferroni correction was used, but does not report the exact family of comparisons or the adjusted results.
How should measurement variability be read?
The endpoint is summarized as a mean and standard deviation. A mean represents the average measured value, and a standard deviation describes the spread of individual measurements around that average. A standard deviation is not a confidence interval and does not directly describe the precision of a comparison between conditions. For a paired design, the variability of within-participant differences is especially relevant to the precision of a paired contrast. Those difference summaries are not reported in the registry record.
The measurements span multiple frequencies, so general statistical interpretation should consider whether the analysis treats frequency as a separate outcome, a repeated factor, or a basis for multiple comparisons. The registry describes measurements across frequencies from 250-8000Hz and notes comparisons across earmold types, but does not report the full frequency-specific modeling strategy. No assumptions about that strategy can be made from the brief method description alone.
10. Multiplicity, Missing Data and Analysis Populations
The endpoint description includes measurements across frequencies and comparisons among three earmold types. Multiple conditions and frequency-specific outcomes can create multiple opportunities for statistical testing. The registry states that post-hoc paired t-tests with Bonferroni correction were used to compare earmold material types. This indicates that some adjustment for multiple comparisons was planned or used, but the precise set of comparisons covered by the correction is not reported in the registry record. The correction’s results are also not reported.
The registry lists four outcome measures and four analyses, but does not provide their detailed definitions or numerical results in the available record. The primary endpoint description covers real-ear acoustic measurements. Subjective ratings of sound quality and physical comfort are mentioned in the study summary, but their measurement instruments and analysis details are not reported in the registry record. The distinction between primary and other outcome analyses therefore cannot be fully assessed from the record alone.
Missing-data handling and analysis populations are not reported in the registry record. It is not stated whether all enrolled participants completed every earmold condition, how incomplete or unusable measurements were handled, or whether any participants were excluded from an analysis. The registry also does not report whether analyses followed an intention-to-treat, per-protocol, or other defined population.
As a general statistical consideration, missing observations can affect repeated-measures comparisons if the likelihood of missingness is related to participant characteristics or measured outcomes. The impact depends on the amount and pattern of missingness and on the analysis method. Without a participant flow or missing-data account, the extent of this issue cannot be evaluated.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| 3rd Party Control, Then In-house_PLA, Then In-house_Resin | 0 | 30 | 0.0% |
| In-house_Resin, Then 3rd Party Control, Then In-house_PLA | 0 | 30 | 0.0% |
| In-house_PLA, Then In-house_Resin, Then 3rd Party Control | 0 | 30 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| 3rd Party Control, Then In-house_PLA, Then In-house_Resin | 0 of 30 |
| In-house_Resin, Then 3rd Party Control, Then In-house_PLA | 0 of 30 |
| In-house_PLA, Then In-house_Resin, Then 3rd Party Control | 0 of 30 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| 3rd Party Control, Then In-house_PLA, Then In-house_Resin | 0 of 30 |
| In-house_Resin, Then 3rd Party Control, Then In-house_PLA | 0 of 30 |
| In-house_PLA, Then In-house_Resin, Then 3rd Party Control | 0 of 30 |
The registry lists serious adverse events, other adverse events, and deaths for each of the three earmold-order groups. In each listed group, 30 participants are recorded as at risk, with 0 serious adverse events, 0 other adverse events, and 0 deaths. No serious adverse event terms are listed.
These entries describe the safety counts recorded in the registry for the listed groups. They do not establish that no adverse experiences occurred outside the categories or reporting procedures represented in the record. Zero recorded events also do not show that the underlying risk is zero; they indicate that no events in those categories are reported for the listed groups.
The same at-risk count appears for each sequence group, but the registry record does not explain the relationship between these entries and the total enrollment. The group counts should therefore be read as listed, not added to infer a total number of unique participants. Details on adverse-event collection, follow-up duration, severity definitions, and attribution to an earmold type are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The study addresses a focused measurement question: whether real-ear acoustic measurements differ across a third-party acrylic control earmold and in-house resin and PLA earmolds when tested with a hearing aid. Its randomized crossover structure allows measurements from different earmold conditions to be compared within participants. The registry describes objective acoustic measurement and also mentions subjective sound-quality and physical-comfort ratings.
The record does not report numerical findings for the primary endpoint. As a result, it does not support a description of the direction, size, or precision of the differences between earmold types. It also does not report a threshold for judging whether an acoustic difference is practically important. Study completion and a defined analysis method do not reveal what the estimates were.
The findings, if interpreted from a full results record, would apply to the conditions tested: participants described as having normal hearing, hearing aids programmed to simulate a specified hearing loss, and the earmold fabrication approaches described. The registry does not report enough information to assess how well the participants represent other populations or how the tested conditions relate to other fitting contexts.
The listed safety entries show zero recorded serious and other adverse events and zero deaths in each sequence group. They should be understood as registry counts, not proof that an event is impossible or that every kind of discomfort was absent. The study summary specifically identifies physical comfort as a subjective outcome, while detailed comfort results are not reported in the registry record.
Overall, the record establishes the study question, crossover design, primary measurement, and named analysis methods. It does not provide the numerical outcome evidence needed to judge the observed acoustic contrasts or their uncertainty. No conclusion about an earmold’s performance should be inferred from the design description alone.
13. Why This Trial Matters Statistically
This trial is statistically notable for using a crossover structure to compare device conditions within participants. In general, within-participant designs can reduce the influence of stable between-person variation because each participant serves as their own reference across conditions. That feature is relevant when measurements can be repeated under different earmold types and when the outcome is measured objectively in the ear canal.
The order of conditions also matters in a crossover study. The registry lists three sequences, which indicates that participants did not all undergo the same listed order. Sequence variation can help address order effects when the design and analysis are appropriately planned. The record does not report how sequence allocation was implemented or whether period and carryover effects were included in the analysis, so the protection against those effects cannot be evaluated.
The trial also illustrates why method labels are not enough for full statistical interpretation. Repeated-measures analysis of variance and paired comparisons are named, and Bonferroni correction is noted. But readers also need estimates, uncertainty measures, and clear information about the comparison families and frequency-specific analyses to understand the results. Those numerical findings and details are not reported in the registry record.
Finally, objective acoustic measurements and subjective experience answer related but distinct questions. Real-ear measures characterize sound in the ear canal under the test conditions; ratings of sound quality and comfort reflect participants’ reported experience. The study summary identifies both kinds of assessment, but the detailed results and methods for the subjective ratings are not reported in the registry record. Keeping those evidence types distinct is important when interpreting a device comparison.
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 main limitation for interpreting the registry record is the absence of numerical primary-outcome results. Means, standard deviations, contrasts, confidence intervals, and p-values are not reported in the registry record. Without them, the magnitude, direction, and precision of the acoustic comparisons cannot be assessed.
The endpoint involves measurements across multiple frequencies, but the detailed frequency-specific analysis strategy is not reported. The record does not explain whether frequencies were analyzed separately, combined, or modeled jointly, and it does not give the exact scope of the Bonferroni correction. Those details matter for interpreting multiple comparisons and the meaning of any overall result.
The design uses repeated measurements, and the registry lists different condition sequences. However, details about sequence allocation, period effects, carryover, and their treatment in the analysis are not reported in the registry record. The record also does not describe missing measurements, participant flow through all conditions, or the population included in each analysis.
Participant eligibility beyond the description of normal hearing, baseline characteristics, and the measurement instruments for subjective outcomes are not reported in the registry record. The study summary mentions sound-quality and physical-comfort ratings, but detailed results for those outcomes are not available in the registry record described. The scope of inference is therefore limited to the testing conditions and population as described, and generalizability cannot be assessed fully.
The adverse-event entries list zero events in each sequence group, but definitions, collection procedures, follow-up, and attribution methods are not reported. These limitations do not negate the stated design; they define what can and cannot be concluded from the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Investigations of Ear Tip Performance, Perceptions, and Experiences — NCT05725824.
- Registry record last updated 2024-07-29; status last verified 2024-07.
- Results first posted 2024-07-29.
- 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.
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18. Record Summary
The registry record identifies NCT05725824 as a completed, randomized, unmasked crossover study titled “Investigations of Ear Tip Performance, Perceptions, and Experiences.” The sponsor was the University of Arizona. Enrollment was 30, with a start date of 2023-07-30 and a primary completion date of 2024-01-17.
The study compared a third-party acrylic control earmold with in-house resin and PLA earmolds in participants described as having normal hearing. The primary endpoint was Real Ear Measures, recorded in dB SPL and summarized as a mean with standard deviation. The registry describes repeated-measures analysis of variance and post-hoc paired t-tests with Bonferroni correction.
Numerical results for the primary endpoint, detailed missing-data methods, and detailed analysis-population definitions are not reported in the registry record. The safety entries list 0 serious adverse events, 0 other adverse events, and 0 deaths in each of the three sequence groups.