Retrieval-Based Word Learning in Developmental Language Disorder During Book Reading: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Retrieval-Based Word Learning in Developmental Language Disorder During Book Reading (NCT06026124), a non-randomized na study. The primary outcome is Word Form Accuracy (Number of Words Correctly Recalled) in Repeated Spaced Retrieval (RSR) and Repeated Study (RS) Conditions at 5 Mins..

2. Clinical Question

The clinical question is educational and developmental rather than a question about a medical treatment. The registry identifies DLD and typical language development as the participant groups, and repeated spaced retrieval and repeated study as the learning conditions. Its non-randomized designation matters for interpretation: differences between groups or conditions cannot automatically be attributed to the learning approach, because the record does not establish randomized assignment or a like-for-like control comparison. The registry lists a factorial model, but the specific factors, their levels, and the analysis structure are not reported in the registry record. The question therefore has a clearly defined learning outcome and learning conditions, but the record does not supply the results needed to determine the observed pattern of recall or the precision of any difference.

3. Trial Design

The registry record describes a completed, non-randomized behavioral study sponsored by Purdue University. Its listed model is factorial and masking is listed as none. The record reports enrollment of 27 participants and identifies children with DLD and children with typical language development as the two groups. It also lists two learning conditions: Repeated Spaced Retrieval and Repeated Study. Because allocation is non-randomized, the registry explicitly cautions that the arms are not a like-for-like control comparison.

The study’s stated focus is word learning among four- and five-year-old children with DLD, with comparison to children whose language development is typical for their age. The intervention descriptions concern learning procedures, not a drug or device. In RSR, spaced retrieval trials occur; in RS, the child has no retrieval trials. The primary endpoint description places recall testing 5 minutes after the second learning session.

The registry records a start date of 2022-10-31, a primary completion date of 2024-09-17, and a status of completed. The phase is listed as not applicable. These administrative details describe the registered study, but they do not provide evidence about the size or direction of a learning effect.

Important design details are not reported in the registry record. These include the exact allocation process, whether each child experienced both learning conditions, how the factorial structure was implemented, and the planned statistical model. The record also does not describe an interim-analysis plan or a sample-size justification. Those omissions limit reconstruction of the design and analysis from the registry alone. In particular, the non-randomized designation means that any comparison should be read with attention to possible differences between participants or conditions, rather than as if assignment had guaranteed comparable groups.

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: Children are initially tested to see if they meet the inclusionary and exclusionary criteria of Developmental Language Disorder. These include falling below age level on a language test, while passing a hearing screening, a non-verbal IQ test, and an autism screener. Many children who are recruited and consented do not meet all these criteria pointing to the fact that DLD is not readily recognizable to non-professionals (parents, preschool teachers).

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 Word Form Accuracy (Number of Words Correctly Recalled) in Repeated Spaced Retrieval (RSR) and Repeated Study (RS) Conditions at 5 Mins., measured over 5 minutes after end of learning period.

The primary endpoint is word-form accuracy, defined as the number of novel words correctly recalled. The registry describes testing 5 minutes after the second learning session. For each condition, four verbs were tested twice, producing 8 recall items. The child was asked to recall and say the word associated with each novel referent. The endpoint is a count of correct responses, with the registry specifying a mean and standard error as the summary measure.

This endpoint targets recall of the word form shortly after learning, rather than broad language ability or long-term retention. It is relevant to the stated study question because the learning procedures differ in whether children practise retrieving newly introduced words. A count of correct items can indicate how many of the tested words a child recalls under each learning condition. Comparing condition-level means can describe average performance, while a standard error describes uncertainty around an estimated mean; it is not a measure of how much individual children vary.

The endpoint has a defined testing time and a bounded set of items, which helps specify what the score represents. However, the registry record does not report the observed means, standard errors, condition contrast, confidence interval, or statistical test. It therefore does not establish how many words children recalled, whether scores differed between conditions, or how precisely any difference was estimated. The short interval also means the endpoint should be interpreted as immediate recall at the stated assessment time, not as evidence about retention over longer periods or language learning in everyday settings.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary measure is continuous in the broad sense that it summarizes a numerical score, although the score itself is a count of correct recall items. The registry specifies the mean as the parameter and the standard error as the dispersion measure. A mean describes the average score in a group or condition. A standard error describes how precisely an estimated mean is determined from the data under the analysis; it is not the same as the spread of scores among individual children. The observed mean and standard error are not reported in the registry record, so the endpoint’s numerical distribution cannot be assessed.

What does the endpoint capture?

The endpoint is the number of words correctly recalled 5 minutes after the second learning session. Four verbs are tested twice per condition, for 8 recall items in each condition. The score therefore captures performance on the specified recall task at that assessment time. It does not, by itself, represent broad language ability or retention over a longer period. General statistical point: a narrowly defined outcome can make a comparison easier to interpret, while also limiting how widely the result can be generalized beyond the task and timing that were measured.

Why does the allocation matter?

The study is listed as non-randomized, and the registry cautions that the arms are not a like-for-like control comparison. Random assignment, when used, is intended to reduce systematic differences between groups; that protection cannot be assumed for a non-randomized design. General statistical point: observed differences in such designs may reflect the intervention, differences in the participants, or other features of how the comparison was formed. The registry does not report the allocation procedure, so the extent or direction of possible imbalance cannot be evaluated from this record.

The registry also lists a factorial model. In general, a factorial design can assess more than one factor and can examine whether effects vary across combinations of factor levels. But the names and levels of the factors, the exact comparison structure, and the statistical model are not reported in the registry record. The factorial label alone does not reveal which contrasts were planned or how the dependence among observations, if any, was handled.

How should uncertainty be understood?

A confidence interval, when reported, gives a range of values compatible with the data and model at a stated confidence level. Its width reflects precision: wider intervals indicate less precise estimation, while narrower intervals indicate greater precision. No confidence interval or confidence level for the primary contrast is reported in the registry record. A p-value, if reported, would address how compatible the data are with a specified null hypothesis under the statistical model; it would not measure the size or educational importance of a difference. No p-value for the primary comparison is reported in the registry record.

General statistical point: counts may have non-normal or bounded distributions, particularly when possible scores are limited to a fixed number of items. The appropriate analysis depends on the score distribution and design. The registry does not report the planned or conducted model, distributional checks, or any treatment of repeated measurements. It is therefore not possible to determine from the record whether the analysis used a model suited to the count structure, or how it handled observations that could be related within a child.

What does the planning illustration mean?

The sample-size material is described as a planning illustration based on the observed effect, not as the trial’s own design justification. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. Such calculations describe hypothetical sample sizes under assumptions. They are not observed power and do not show that the trial was designed with those assumptions. The registry record does not report the study’s own sample-size justification, and the observed effect needed to interpret the illustration’s scale is not reported in the registry record.

General statistical point: power calculations depend on the assumed effect, variability, allocation, and analysis. A planning calculation based on an observed effect is especially dependent on the estimate used: an imprecise observed effect can make the resulting illustration uncertain. It should not be used as evidence that a study’s actual sample was adequate or that a result is reliable. The registry reports enrollment of 27, but does not report an outcome-specific calculation or analysis population.

What does the record allow readers to verify?

The registry reports 7 outcome measures and 12 analyses, but detailed analysis specifications and results are not reported in the registry record. The outcome count and analysis count do not disclose which tests were conducted, how outcomes were related to hypotheses, or which results were designated primary beyond the stated endpoint. Recalculation from summary statistics is not possible because the primary summary statistics and contrast are not reported in the registry record. Overall, the record supports interpretation of the outcome definition and broad design, but not verification of the statistical result or its precision.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 7 outcome measures and 12 analyses. It identifies the primary endpoint as word-form accuracy and names the Peabody Picture Vocabulary Test, Fourth Edition, and Years of Maternal Education among secondary outcomes. The specific analysis-to-outcome mapping, planned contrasts, and any hierarchy of hypotheses are not reported in the registry record. Nor is an adjustment strategy for multiple comparisons reported in the registry record.

General statistical point: when many outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase. Procedures for handling multiplicity can address that concern, but the choice depends on the study’s questions and analysis plan. Without the planned testing structure, it is not possible to determine whether multiplicity adjustment was needed or whether any adjustment was used. The number of analyses alone does not establish that results were selectively reported.

Missing-data handling and analysis populations are also not reported in the registry record. The enrollment count is 27, but the record does not state how many participants contributed to each primary or secondary analysis, whether any endpoint observations were missing, or how missing observations were handled. It does not report whether analyses followed an intention-to-treat, per-protocol, or other population definition. These details matter because exclusions and missing outcomes can affect estimates and their precision, particularly in a non-randomized study.

The record does not describe interim analyses, stopping rules, or a prespecified statistical analysis plan. These details are not reported in the registry record, so no conclusions about their use can be drawn.

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 summaries list 13 children with DLD and 14 children with typical language development. In both groups, the record reports 0 serious events, 0 other events, and 0 deaths. These are the counts shown in the registry’s safety summaries; no serious-event terms are listed.

These figures should be read as reported counts, not as proof that no events could have occurred outside the way the registry captured or summarized them. The record does not describe the event-collection procedures, observation period for safety, or definitions used for other events. It also does not report a separate safety analysis or explain whether the displayed group counts include every enrolled participant. Those details are not reported in the registry record.

Because this is a behavioral word-learning study and the safety summaries contain no reported events, the figures provide a limited description of the registry’s recorded safety information. They do not establish the absence of all possible harms, and they do not answer the primary learning question. No rate calculations are needed to read the posted counts; the registry reports the counts directly.

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

The registry record documents a study of repeated retrieval during book-based word learning, with a comparison condition involving repeated study and no retrieval trials. Its primary outcome is a count of correctly recalled words at a defined short-term assessment. The stated rationale is to examine whether retrieval practice may benefit word learning in children with DLD and to study learning in a story-book context.

However, the registry does not report the primary outcome results. It therefore does not show whether recall was higher in RSR or RS, how large any difference was, or how precisely it was estimated. No conclusion about a benefit, lack of benefit, or equivalence between conditions can be drawn from the registry record alone. A study aim is not a finding.

Even if a result were available, the non-randomized design would remain important. The record explicitly cautions that the arms are not a like-for-like control comparison. General statistical point: without randomized allocation, a measured difference can be entangled with differences between participants or with other design features. The registry does not provide enough allocation or analysis detail to assess those possibilities.

The endpoint is also limited in scope. It concerns recall of four verbs tested twice per condition, 5 minutes after the second learning session. It does not establish long-term retention, learning of other kinds of words, broad language development, academic performance, or social and economic outcomes. Those broader topics appear in the background rationale, but are not outcomes reported in the registry record.

The registry lists secondary measures of receptive vocabulary and maternal education, but their results are not reported in the registry record. Thus the record describes the question and measurement framework, not an answer about the effectiveness or real-world value of either learning approach. Interpretation of any fuller evidence would require the actual outcome estimates, their uncertainty, and details of the analysis and participant flow.

13. Why This Trial Matters Statistically

This study raises a useful statistical question: how should learning be evaluated when the outcome is immediate recall of newly introduced words, and when retrieval practice is compared with exposure without retrieval? The endpoint is concrete: the number of words correctly recalled at a specified time, based on a fixed set of recall items. That makes the target of measurement understandable and closely aligned with the stated learning question.

The design also illustrates why statistical interpretation depends on more than an outcome definition. The registry labels the study non-randomized and warns that its arms are not a like-for-like control comparison. That makes the distinction between describing scores and attributing a difference to a learning condition especially important. The factorial designation adds another layer, but the record does not report the factors, contrasts, or model needed to understand that structure fully.

The sample-size material is identified as a planning illustration rather than the study’s own design justification. This distinction is important: hypothetical planning calculations and observed study results answer different questions. A planning illustration is not evidence of adequate precision in the completed study, and it is not observed power.

Most importantly, the record defines a focused primary outcome but does not report its results. That absence limits what can be learned statistically from the registry entry. Readers can identify the target population, learning conditions, endpoint, and broad design, but cannot evaluate an effect estimate, its uncertainty, or the consistency of results across language-development groups. The case therefore highlights both the value of precise outcome definitions and the need for transparent results and analysis details before drawing conclusions.

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 this registry record is that primary and secondary outcome results are not reported in the registry record. Without score summaries or a comparison estimate, the learning outcomes and their precision cannot be assessed. The record also does not report confidence intervals, statistical tests, or the model used for the primary analysis.

The non-randomized allocation is a further limitation. The registry explicitly cautions that the arms are not a like-for-like control comparison. The allocation procedure and the way participants encountered the two learning conditions are not reported in the registry record, so possible baseline differences and the structure of within-child or between-group comparisons cannot be evaluated.

The endpoint captures short-term recall 5 minutes after the second learning session, using four verbs tested twice per condition. This is a defined but narrow measure. The registry does not report longer-term assessments or outcomes that would show whether the learning carries over to other words, contexts, or everyday communication. The factorial model is listed, but the factors and analysis structure are not reported in the registry record.

Participant flow, analysis populations, missing data, and outcome-specific sample sizes are not reported in the registry record. The record also does not report the study’s own sample-size justification, a multiplicity strategy, interim analyses, or a detailed statistical analysis plan. These omissions limit assessment of precision, potential selection effects, and the interpretation of multiple analyses. The listed enrollment and safety-group counts do not resolve those questions.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Retrieval-Based Word Learning in Developmental Language Disorder During Book Reading — NCT06026124.
• Registry record last updated 2026-09-03; status last verified 2026-09.
• Results first posted 2025-08-28.
• 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

The registry describes a completed, non-randomized behavioral study of word learning during book reading, sponsored by Purdue University. It lists 27 participants, children with DLD and children with typical language development, and two learning conditions: Repeated Spaced Retrieval and Repeated Study. The primary endpoint is the number of words correctly recalled 5 minutes after the second learning session, with 8 recall items per condition.

The record identifies a factorial model and no masking, but does not report the allocation procedure, detailed analysis plan, or the specific factorial structure. It lists 7 outcome measures and 12 analyses, including secondary outcomes of the Peabody Picture Vocabulary Test, Fourth Edition, and Years of Maternal Education. Primary and secondary outcome results are not reported in the registry record. Safety summaries list 0 serious events, 0 other events, and 0 deaths in each of the two language-development groups.