Screening for Hesitancy to Optimize Talk: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Screening for Hesitancy to Optimize Talk (NCT02708745), a randomized na study. The primary outcome is Child's Mean Percent Days Under-immunized.

2. Clinical Question

The primary endpoint concerns children’s immunization status, while the assigned surveys were received by parent participants. The registry describes the primary comparison as the mean percent days under-immunized among children of parents who received versus did not receive the intervention. The intervention and placebo arms provide the two survey conditions for that comparison.

The study’s stated overall goal was to determine whether incorporating a novel parent-report measure of vaccine hesitancy into pediatric primary care could improve acceptance of childhood vaccines among vaccine-hesitant parents. The recorded primary outcome is a child-level measure of under-immunization through 8 months of age, rather than a direct measure of parent attitudes or vaccine acceptance. The registry also lists parent visit experience and provider perceptions of barriers to vaccine discussion as secondary outcomes. Their detailed results are not reported in the registry record.

3. Trial Design

The registry describes SHOT as a randomized, triple-masked, parallel-design study. It lists an enrollment of 562 and the sponsor as Seattle Children's Hospital. The study began in 2016-03, had a primary completion date of 2018-06-11, and is recorded as completed. The listed phase is NA.

Parents in the intervention arm received a survey about attitudes toward childhood vaccines before their child’s health supervision visit. Parents in the placebo arm received a survey about attitudes toward common child health topics before the visit. Both interventions are classified as behavioral. The registry does not explain who was masked, how masking was maintained, or how the survey assignments were generated.

The record identifies the design as cluster-randomized. That feature matters to interpretation: observations within a cluster may be related, so treating every individual observation as independent can give misleading uncertainty estimates. The registry explicitly indicates that a simple individual-level re-analysis would be misleading and that only the sponsor’s own analysis is shown. The cluster definition, cluster count, and allocation details are not reported in the registry record.

The enrollment figure does not establish how many children or parents contributed data to the primary analysis, nor how many were in each arm. Arm-specific analysis counts and participant flow are not reported in the registry record. The registry also does not report a sample-size justification or enough details to assess whether the planned analysis accounted for clustering. The sample-size assumptions described for planning illustrations are not the trial’s design assumptions; those illustrations use equal allocation, a two-sided significance level of 0.05, and a normal approximation.

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

Analysis population for the primary outcome, as defined in the registry: Mean percent days under-immunized of child participants by study arm

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: In 'placebo arm' and 'intervention arm': parent/child dyads; In 'pre-intervention providers' group: providers at enrolled clinics who completed a survey before the parent-level intervention; In 'post-intervention providers' group: providers at enrolled clinics who completed a survey after the parent-level intervention

6. Primary Endpoint

The registry lists the primary outcome as Child's Mean Percent Days Under-immunized, measured over Child's immunization status at 8 months of age.

The primary endpoint is the child’s mean percent days under-immunized, measured at 8 months of age. Its unit is a percentage of days under-immunized, and the registry specifies a mean as the summary measure. It is intended to represent children’s immunization status over time rather than a single status assessment on one day. The exact rules used to classify days as under-immunized are not reported in the registry record.

Using a mean provides a group-level summary of this continuous measure that can be compared between the survey arms. The endpoint connects the intervention’s parent-report measure to a child immunization outcome, consistent with the study’s stated goal of improving acceptance of childhood vaccines. It is not itself a direct measure of parent hesitancy, provider communication, or visit experience; those topics are addressed separately in the registry’s secondary outcomes.

The outcome is listed for children of parents who received versus did not receive the intervention. The recorded timeframe is child immunization status at 8 months of age. Although the registry identifies a 95% confidence interval as the intended dispersion measure, the reported analysis contains no group means, estimated difference, or confidence interval. Those quantities are not reported in the registry record, so the magnitude and precision of the between-arm difference cannot be assessed from the posted result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous and summarized as a mean. The registry reports a two-sided t-test for the comparison between study arms. In general, a t-test evaluates whether observed group means are compatible with a null hypothesis of no difference, using the variability in the data to quantify uncertainty. A two-sided test allows evidence in either direction rather than testing only whether one arm is higher or lower.

The reported result is p = .29. In general, a p-value is calculated under a null model and analysis assumptions; it describes how unusual data at least as discrepant as those observed would be under that model. It is not an effect estimate, a measure of clinical importance, or the probability that the null hypothesis is correct. Because the record gives no group means or estimated difference, the direction and magnitude of the primary contrast cannot be determined from the p-value.

A confidence interval gives a range of values compatible with the data and the specified method, conveying uncertainty around an estimate. The registry identifies a 95% confidence interval as the intended dispersion measure for the primary outcome, but the reported analysis has no interval limits or point estimate. The interval and its interpretation are therefore not reported in the registry record. Without them, it is not possible to judge how precisely the trial estimated the difference.

The study is identified as cluster-randomized. In general, cluster randomization assigns groups rather than treating each person as an independent assignment unit. Outcomes from people in the same group can be correlated because they share circumstances or exposure. When this dependence is ignored, the apparent amount of independent information can be overstated and uncertainty can be misrepresented. The registry specifically cautions that a simple individual-level re-analysis would be misleading and states that only the sponsor’s own analysis is shown. The record does not describe the clustering unit or the method used to account for clustering in that analysis.

The registry lists a superiority analysis. In general, a superiority test asks whether the data support a difference in a specified direction or either direction, depending on the test, rather than establishing equivalence. A non-significant test does not demonstrate that two conditions are equivalent. Equivalence or non-inferiority questions require appropriate margins and analysis plans; those are not reported in the registry record.

Sample-size illustrations are planning calculations, not observed results and not observed power. The stated assumptions for those illustrations include a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a stated fraction of the observed effect. The record says the illustrations are not the trial’s own design. A sample-size calculation under such assumptions can show how a hypothetical study might be planned, but it does not establish how the actual trial was designed or how much power it had. The trial’s sample-size justification is not reported in the registry record.

In general, over-dispersion means that the observed variability is greater than a model assumes. When present, accounting for it can change uncertainty estimates and tests. The record does not report an over-dispersion assessment, so none can be inferred for this outcome. Similarly, details such as the exact model specification, adjustment variables, handling of missing outcomes, and analysis population are not reported in the registry record. These omissions limit independent evaluation of the reported test.

There are 3 listed outcome measures and 3 listed analyses. In general, when several outcomes or tests are considered, the chance of at least one apparently unusual result can increase unless the analysis plan addresses multiplicity. The record does not report whether a multiplicity adjustment was used or how the primary outcome was prioritized relative to other analyses. The listed p-value should therefore be interpreted as the reported result for its analysis, not as a complete account of all possible testing decisions.

10. Analyses Reported by the Sponsor

The posted primary analysis reports a two-sided t-test with p = .29. It does not include the arm means, an estimated difference, or a confidence interval, so there is no numerical effect estimate to compare with an independent recalculation. The registry identifies the study as cluster-randomized and explicitly cautions that a simple individual-level re-analysis would be misleading. It states that only the sponsor’s own analysis is shown.

Accordingly, the posted result should be read as the sponsor analysis recorded for this clustered study, not as an individual-level reconstruction from summary data. The registry does not provide enough outcome summaries or analysis details to reproduce the test or assess the effect of clustering independently. The p-value indicates the reported test result, but it cannot stand in for the missing estimate and confidence interval. The analysis method used to account for the cluster structure is not reported in the registry record.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures and 3 analyses. It identifies the child’s mean percent days under-immunized as the primary outcome and lists parent visit experience and provider perceptions of barriers to vaccine discussion as secondary outcomes. The detailed results for those secondary outcomes are not reported in the registry record.

When a study examines several outcomes or performs several analyses, multiplicity can make isolated results harder to interpret. In general, an analysis plan may specify which outcome is primary and whether any adjustment or testing hierarchy will be used. The registry record does not report whether a multiplicity adjustment was planned or applied, nor does it describe the relationship among the listed analyses. The reported primary p-value should be understood as the result for that analysis, without assuming that it accounts for all other outcomes or tests.

The registry does not report the number of participants with primary outcome data, the analysis population, or how missing observations were handled. It does not describe imputation, exclusions, or sensitivity analyses for missing data. These details matter because the analyzed group and the handling of unavailable outcomes can affect the interpretation of an estimate. Enrollment of 562 does not, on its own, establish how many participants contributed to the primary analysis or whether outcome data were complete.

The record identifies a cluster-randomized design and warns against a simple individual-level re-analysis. However, the cluster definition, the number of clusters, and the analysis population by cluster are not reported in the registry record. The details needed to evaluate clustering, missingness, and multiplicity are therefore not available in the posted result.

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.

The registry reports no serious adverse events and no deaths in the listed groups. For the Placebo Arm, 91 were at risk for serious adverse events and 0 were affected; 91 were at risk for other adverse events and 0 were affected, with 0 deaths. For the Intervention Arm, the corresponding at-risk counts are 65 and 65, with 0 affected in each category and 0 deaths.

The registry also lists Pre-Intervention Providers, with 121 at risk in each adverse-event category, 0 affected, and 0 deaths; and Post-Intervention Providers, with 116 at risk in each category, 0 affected, and 0 deaths. These provider groups are listed separately from the parent survey arms and should not be conflated with them.

These figures describe the recorded event counts for the groups and at-risk counts shown. They do not establish that no events occurred outside the registry’s definitions or observation period. The adverse-event definitions, collection period, and follow-up details are not reported in the registry record. The figures should therefore be read as the posted safety counts, not as a broader guarantee about safety.

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

The posted primary result is a two-sided test with p = .29 for the comparison of mean percent days under-immunized at 8 months of age. It does not show a statistically detectable difference under that reported test. That is a limited statement about the test result, not proof that the intervention and placebo conditions produced the same outcome.

The registry does not report the group means, the estimated difference, or its confidence interval. Without those values, readers cannot determine which arm had a higher mean, how large the observed contrast was, or how precisely it was estimated. A p-value by itself cannot establish that an important difference has been excluded. Nor does it indicate the probability that the intervention is effective or ineffective.

The study’s stated goal concerned integrating a parent-report measure of vaccine hesitancy into pediatric primary care and improving acceptance of childhood vaccines among vaccine-hesitant parents. The primary endpoint is a child immunization measure, while the intervention was a parent survey. The endpoint therefore addresses a downstream outcome relevant to the study goal, but it is not a direct measure of vaccine acceptance or parent hesitancy. The registry’s secondary outcomes address visit experience and provider perceptions, but their results are not reported in the registry record.

The clustered design is also central to interpretation. The record cautions against a simple individual-level re-analysis and reports only the sponsor’s own analysis. The analysis details needed to assess how the cluster structure was handled are not reported in the registry record. The posted p-value should be interpreted within that limitation.

In short, the record documents the trial design, primary outcome, and a test result, but it does not provide enough numerical detail to quantify the primary effect or its precision. It does not support a claim of equivalence, nor does it by itself resolve the broader question of vaccine acceptance.

14. Why This Trial Matters Statistically

SHOT illustrates why a test result should not be read in isolation. The reported p = .29 gives a test outcome, but the absence of group means, an estimated difference, and a confidence interval leaves the size, direction, and precision of the primary comparison unknown. Those quantities are necessary for a fuller statistical interpretation.

The trial also makes the design structure important. It is identified as cluster-randomized, and the registry warns that an individual-level re-analysis would be misleading. This is a useful reminder that the assignment structure affects how uncertainty should be estimated. A familiar test name, such as a t-test, does not by itself reveal whether the reported analysis adequately reflects clustering; the registry does not provide those details.

The endpoint connects a parent-focused survey intervention to a child-level measure of immunization status at 8 months of age. That distinction matters when interpreting what the primary result represents. It is a measure of children’s under-immunized days, not a direct score of parent attitudes or provider communication. The registry separately lists parent visit experience and provider perceptions as secondary outcomes.

Finally, the study shows the value of separating a trial’s stated objective from the information available in its results record. A completed randomized study and a reported p-value do not alone establish the magnitude or practical importance of an effect. Effect estimates, uncertainty intervals, analysis details, and outcome reporting all contribute to a sound statistical reading.

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 limitations constrain interpretation of the posted result. The registry identifies a cluster-randomized design but does not report the cluster definition, number of clusters, or how the sponsor’s analysis accounted for clustering. It explicitly cautions that simple individual-level re-analysis would be misleading, so the reported result cannot be independently reconstructed from the information in the record.

The primary analysis includes a two-sided t-test result of p = .29, but no arm-specific means, estimated difference, confidence interval, or analysis counts. The direction, magnitude, and precision of the primary contrast are therefore not reported in the registry record. The record also does not describe the outcome classification rules used to calculate percent days under-immunized.

Although enrollment is listed as 562, the number contributing data to the primary analysis and the distribution across arms are not reported. Participant flow, missing-data handling, analysis-population definitions, and sensitivity analyses are not reported in the registry record. The record also does not provide a sample-size justification for the trial; the stated sample-size illustrations are explicitly not the trial’s own design.

The registry lists 3 outcome measures and 3 analyses, but it does not report whether multiplicity was addressed. Detailed results for the listed secondary outcomes are not reported in the registry record. Masking is listed as triple, but the roles masked and the procedures used to maintain masking are not described. Eligibility criteria and further details of the study population are also not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Screening for Hesitancy to Optimize Talk — NCT02708745.
• Registry record last updated 2019-10-01; status last verified 2019-09.
• Results first posted 2019-10-01.
• 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

Screening for Hesitancy to Optimize Talk (SHOT) is recorded as a completed randomized, triple-masked, parallel study sponsored by Seattle Children's Hospital. The registry lists enrollment of 562, a start date of 2016-03, and primary completion on 2018-06-11. The interventions were behavioral surveys administered to parent participants before a child’s health supervision visit: a survey about childhood vaccine attitudes or a placebo survey about common child health topics.

The primary outcome was the child’s mean percent days under-immunized at 8 months of age. The reported primary analysis is a two-sided t-test with p = .29. Group estimates and a confidence interval are not reported in the registry record. The record identifies the design as cluster-randomized and cautions that individual-level re-analysis would be misleading. It also lists secondary outcomes concerning parent visit experience and provider perceptions of barriers to vaccine discussion; their detailed results are not reported in the registry record.