Kokkerelli Learning Street Effect Evaluation: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Kokkerelli Learning Street Effect Evaluation (NCT04190680), a non-randomized na study. The primary outcome is Change From Baseline Fruit and Vegetable Knowledge at 3 Months After the Evaluation Lesson.

2. Clinical Question

The study’s focus is on determinants of fruit and vegetable intake as well as intake itself. Knowledge is the primary outcome, but the broader evaluation considers whether children’s understanding, preferences, intentions, attitudes and skills change over time. These are distinct outcomes: a change in knowledge would not by itself establish a change in food preferences, preparation ability or consumption.

The timing of the primary endpoint matters to its interpretation. The registry specifies baseline, an assessment directly after the evaluation lesson approximately three weeks after baseline, and a later assessment three months after that lesson. The primary endpoint concerns the later assessment, rather than only the immediate post-lesson response. Numerical findings for this endpoint and the other outcomes are not reported in the registry record.

3. Trial Design

The Kokkerelli Learning Street Effect Evaluation is a completed, parallel-group study with non-randomized allocation and no masking. The registry lists an enrollment of 226. The intervention arm took part in the school-based programme, while classes in the control arm continued their regular curriculum. The study was sponsored by Maastricht University Medical Center.

The programme combines classroom lessons with a visit to a grower's farm and a cooking workshop. Its stated purpose is nutrition education for primary school students in study years 5-8, covering the origins and processing of food and its use in preparing a healthy meal. The study description says that child-reported questionnaires were used to assess relevant determinants of fruit and vegetable intake.

The registry gives a study start date of 2020-03-15 and a primary completion date of 2022-08-31, with status recorded as completed. The planned assessment schedule for the primary outcome includes baseline, an assessment directly after the evaluation lesson approximately three weeks after baseline, and an assessment three months after the evaluation lesson.

Because allocation was not randomized, differences between groups cannot be interpreted as though assignment created comparable groups. The registry explicitly cautions that the arms are not a like-for-like control comparison. Differences in participant or class characteristics, school context or other factors could be associated with both group membership and outcomes; whether any such differences occurred is not reported in the registry record. The record also does not report the allocation procedure, baseline comparability findings or methods used to address potential confounding.

Although the record identifies the study as parallel, it does not give enough information to describe the statistical handling of clustering within classes or schools. A sample-size justification, details of any interim analyses and a prespecified statistical analysis plan are not reported in the registry record. These omissions limit what can be concluded about how the study was designed to estimate effects or control uncertainty.

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

Reasons for not completing this period:

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 Change From Baseline Fruit and Vegetable Knowledge at 3 Months After the Evaluation Lesson, measured over Baseline, directly after the evaluation lesson (approximately three weeks after baseline), three months after the evaluation lesson.

The primary endpoint is change from baseline in fruit and vegetable knowledge, assessed three months after the evaluation lesson. Knowledge is measured using six questions in a child questionnaire. The total score is based on the number of correct answers; the registry describes 0 as indicating low knowledge and 6 as indicating high knowledge. The measure is a score on a scale, and the registry specifies that it is to be summarized as a mean with standard deviation.

A knowledge score is relevant to the programme’s educational purpose: the Learning Street aims to teach children about food and its preparation. Assessing change over time can describe whether questionnaire knowledge differs after participation, while the control group provides a contemporaneous reference under the regular curriculum. Since group allocation was not randomized, a difference between groups would not by itself establish that the programme caused the difference.

The endpoint’s timing distinguishes a later assessment from the assessment directly after the evaluation lesson, which is described as occurring approximately three weeks after baseline. The endpoint therefore concerns knowledge at the three-month follow-up after the lesson, not solely an immediate response. The registry record does not report the group means, standard deviations, changes from baseline, between-group estimate or uncertainty for this primary endpoint. Accordingly, the size and precision of any observed change cannot be described from the reported information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry classifies the primary outcome as a continuous measure summarized by a mean and standard deviation. The score is calculated from correct answers to six knowledge questions. Treating the score as a continuous measure allows the average score in a group to be described and compared across assessment times. The standard deviation describes how dispersed individual scores are around the group mean. It is not a measure of the uncertainty in the mean itself.

What does change from baseline represent?

A change score expresses how a participant’s later measurement differs from that participant’s baseline measurement. A group’s average change can describe the typical within-group pattern, while a comparison of changes between groups can describe whether the patterns differ. The registry names change from baseline at the later assessment as the primary endpoint. It does not report the numerical changes, the between-group contrast or the exact model used to estimate them.

Baseline adjustment and analysis of change scores are related but not identical approaches. In general, an analysis can compare follow-up measurements while accounting for baseline values, or it can calculate change from baseline and compare those changes. The choice affects the model and may affect precision. The registry record does not report which specific method was used, whether any covariates were included or how the repeated assessments were represented in the analysis. No particular method should therefore be attributed to this evaluation.

How should the assessment schedule be understood?

The registry lists baseline, an assessment directly after the evaluation lesson approximately three weeks after baseline, and a later assessment three months after the lesson. The primary endpoint is the change from baseline at the later assessment. The immediate assessment could describe a different time-specific pattern from the later assessment, but the numerical results and the analysis of the different time points are not reported in the registry record. A finding at one assessment would not automatically establish that a pattern persisted at another.

Why does allocation matter statistically?

Random allocation can, in expectation, balance measured and unmeasured characteristics between study arms. That feature is absent in a non-randomized study. Group differences may reflect programme participation, pre-existing differences, or other factors associated with both participation and the measured outcome. Statistical adjustment can address measured factors if they are available and appropriately modeled, but it cannot guarantee removal of unmeasured confounding. The registry cautions that the arms are not a like-for-like control comparison and does not report a confounding-adjustment strategy.

The programme is described as being delivered to classes, but the registry entries do not specify whether the analysis accounted for similarities among children in the same class or school. Such similarities are called clustering. When outcomes within a class are correlated, treating every child as fully independent can understate uncertainty. In general, a model or variance estimator that accounts for clustering may be needed. Whether such an approach was used is not reported in the registry record.

What do uncertainty measures add?

A point estimate describes the estimated size and direction of a contrast. A confidence interval adds information about precision by showing a range of values compatible with the data and the analysis assumptions. A wider interval indicates greater uncertainty than a narrower interval, all else being equal. A p-value is a measure of how unusual the data, or more extreme data, would be under a specified null hypothesis and model. It does not state the probability that the null hypothesis is true, and it does not by itself convey the size or importance of a difference. The registry record does not report a primary outcome estimate, confidence interval or p-value.

Because the endpoint is a bounded score, its possible values run from 0 to 6. The registry nonetheless specifies a mean and standard deviation. General statistical interpretation should keep the score’s limits in mind: the distribution may be constrained near its boundaries, and a mean alone does not show the full pattern of individual scores. The record does not report score distributions or diagnostic checks, so no claim about the suitability of a particular model can be made.

What does the planning illustration tell readers?

The registry describes planning assumptions using a two-sided significance level of 0.05, equal allocation and a normal approximation. It defines planning effects as stated fractions of the observed effect and specifies that non-time-to-event outputs represent participants per arm. These are planning conventions, not evidence that the trial was designed around those assumptions. The registry does not report its own sample-size justification, and the numeric planning outputs and observed effect values are not reported in the registry record. A planning calculation is not observed power and cannot replace an estimate with its uncertainty.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and ten analyses. It describes the primary knowledge endpoint and identifies other study questions involving intentions, attitudes, liking, skills and fruit and vegetable intake. When several outcomes, time points or contrasts are examined, the chance of at least one apparently unusual result can increase if each is assessed separately. Statistical approaches to multiplicity can adjust the interpretation or testing procedure, but no adjustment method is reported in the registry record. The number of analyses alone does not establish which comparisons were planned, how they were grouped, or whether multiplicity was addressed.

The available record details do not describe missing-data amounts, reasons for missingness, questionnaire completion rates at each assessment, or the method used to handle incomplete responses. They also do not report whether analyses used imputation, complete cases or another approach. Missingness can affect estimates if participants with unavailable outcomes differ systematically from those with observed outcomes. Without the relevant counts and methods, the direction or extent of any such influence cannot be assessed.

The analysis population is also not reported in the registry record. It is not stated whether all enrolled children were included in each analysis, whether inclusion depended on completing particular assessments, or how children who changed participation status were handled. These choices affect the population to which an estimate applies.

The record does not report a statistical analysis plan, a sample-size justification for the trial, or interim analyses. The planning illustration described in the registry uses assumptions for an illustrative calculation; it does not establish the study’s prespecified analysis choices. Consequently, the handling of outcome selection, missing observations, analysis populations and repeated assessments remains unclear.

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 reports no serious adverse events in either listed group. The intervention group has 0 serious events among 61 participants at risk, and the control group has 0 among 165 participants at risk. The registry also reports 0 other adverse events among 61 participants at risk in the intervention group and 0 among 165 at risk in the control group. Deaths are recorded as 0 in each group.

These figures describe the adverse-event entries in the registry. They should not be interpreted as proof that no adverse events of any kind occurred outside the recorded categories or observation procedures. The record does not describe how events were solicited, how long safety monitoring continued for each participant, or whether events were assessed for a relationship to the programme. The list of top serious terms is empty.

Zero recorded events do not allow a comparative safety estimate to be characterized with precision, and the non-randomized allocation further limits direct comparisons between arms. The reported figures are descriptive counts, not evidence that the groups had equivalent safety profiles. No medical conclusion about the programme should be drawn from these counts alone.

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

The registry record establishes that the study evaluated a school-based nutrition education programme and selected fruit and vegetable knowledge as its primary outcome. It defines the score, describes the assessment schedule and identifies a control group receiving the regular curriculum. These details clarify what the study set out to examine.

The record does not report numerical primary outcome findings. As a result, it is not possible to state whether knowledge increased, decreased or remained similar, nor to quantify a contrast between the intervention and control groups. The uncertainty around any effect is also not available. The completed status and enrollment figure do not substitute for outcome results.

Even if a numerical group difference were available, non-randomized allocation would remain important. A difference could be associated with programme participation, but it could also reflect pre-existing differences or contextual factors. The registry itself warns that the groups are not a like-for-like control comparison. The information needed to assess adjustment for such factors is not reported.

Knowledge is only one of the constructs named in the study description. Intentions, attitudes, liking, preparation skills and fruit and vegetable intake are separate outcomes. Evidence about a knowledge score alone would not establish changes in these other measures or show that children’s intake changed. Conversely, the absence of reported results in the registry should not be interpreted as evidence that the programme had no effect.

The appropriate reading is therefore limited: the registry documents a completed non-randomized evaluation, its educational intervention and its primary measurement plan, but it does not report the numerical results needed to assess the direction, size or precision of the primary outcome. The record also leaves important details about analysis, missing data and multiplicity unspecified.

13. Why This Trial Matters Statistically

This evaluation is statistically instructive because it brings together a clearly described educational intervention and outcomes that range from knowledge to reported behavior. The distinction among these outcomes matters. A questionnaire knowledge score measures one aspect of the programme’s aims; it is not interchangeable with liking, skills, intentions or fruit and vegetable intake.

The non-randomized parallel design makes the comparison especially dependent on how groups were formed and how analysis handled differences between them. The registry’s caution that the arms are not a like-for-like control comparison is essential context for any interpretation. A control group can provide a useful reference, but the existence of a comparison group does not itself ensure comparability.

The endpoint also illustrates why measurement timing needs to be explicit. Baseline, an assessment directly after the evaluation lesson approximately three weeks after baseline, and a later assessment three months after the lesson represent different points in the learning process. The primary endpoint focuses on the later change from baseline. Results at one time point should not be treated as a substitute for results at another.

Finally, the registry record illustrates the difference between a study description and a result report. It provides the design, enrollment, outcome definition and safety counts, but numerical primary outcome estimates and their uncertainty are not reported. Without those estimates, readers cannot judge effect magnitude or precision. Reporting analysis populations, missing-data handling, multiplicity decisions and any adjustment for class-level clustering would also help readers assess the credibility and scope of the findings.

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 most immediate limitation of the available record is the absence of numerical efficacy results. Group means, standard deviations, changes from baseline, between-group estimates and uncertainty measures for the primary endpoint are not reported in the registry record. Findings for the other outcomes are likewise not reported in the registry record, so the programme’s measured effects cannot be characterized.

The non-randomized allocation limits causal interpretation. The registry explicitly says the arms are not a like-for-like control comparison. It does not report how classes entered each group, whether baseline characteristics differed, or what statistical methods were used to address confounding. Without that information, any potential group contrast would need cautious interpretation.

The intervention is delivered to classes, but the record does not specify whether the analyses accounted for dependence among children in the same class or school. It also does not report the analysis population, missing-data frequency or handling, questionnaire response rates, or the statistical treatment of repeated assessments. These omissions make it difficult to evaluate the robustness of estimates even if numerical results were available.

The record lists five outcome measures and ten analyses but does not report a multiplicity strategy or a full analysis plan. It does not provide the trial’s sample-size justification or information about interim analyses. The planning illustration’s assumptions do not fill those design-reporting gaps. Finally, child-reported questionnaires are the stated measurement approach; the record does not describe validation or additional measurement procedures for the outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Kokkerelli Learning Street Effect Evaluation — NCT04190680.
• Registry record last updated 2025-12-16; status last verified 2023-09.
• Results first posted 2025-12-16.
• 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

The Kokkerelli Learning Street Effect Evaluation is a completed, non-randomized parallel-group study sponsored by Maastricht University Medical Center. The registry lists 226 enrolled participants and no masking. The intervention consists of classroom-based lessons, a grower's farm visit and a cooking workshop; the control group continued its regular curriculum.

The primary endpoint is change from baseline in a fruit and vegetable knowledge score three months after the evaluation lesson. The score is based on six questionnaire questions and ranges from 0 to 6 as described in the registry. The study also addresses intentions, attitudes, liking, preparation skills and intake.

The registry reports zero serious and other adverse events and zero deaths in both groups. Numerical primary efficacy results, analysis methods for missing data and the analysis population are not reported in the registry record. The non-randomized comparison requires caution because the registry states that the arms are not a like-for-like control comparison.