Toddler Overweight Prevention Study Among Low-Income Families: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Toddler Overweight Prevention Study Among Low-Income Families (NCT02615158), a randomized na study. The primary outcome is Change of Body Mass Index (BMI) Z-score for Toddlers.

2. Clinical Question

3. Trial Design

The registry record classifies the study as randomized, double-masked, and parallel, with behavioral interventions. It lists an enrollment of 277 and a completed status. The recorded study start is 2006-04, and primary completion is recorded as 2013-09. The record gives the phase as NA.

The parallel design assigned participants to intervention groups that were followed as separate arms. The listed groups were Maternal Physical Activity and Nutrition, Parenting, and Child Safety. The maternal intervention addressed healthy diet and physical activity for mothers. The parenting intervention addressed parenting, limit setting, and development strategies. Child Safety served as an attention control, with safety-focused intervention for parents.

The record labels the study double-masked, but it does not identify who was masked or describe how masking was implemented. The randomization procedure, allocation ratio, and any stratification or blocking are not reported in the registry record. Nor does the record explain how intervention delivery, follow-up, or adherence was monitored.

The stated primary outcome was continuous: change in toddler BMI z-score from baseline to 12-month follow-up, summarized as a mean with standard error. The registry also lists secondary outcomes concerning diet quality for toddlers and mothers, physical activity for children and mothers, and feeding style. It lists 7 outcome measures and 14 analyses, but the details of those analyses are not reported in the registry record. In particular, the record does not give a complete statistical analysis plan or identify which comparisons were prespecified.

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: Toddlers in low-income families, defined as WIC-eligible (income \< 185% of poverty index). WIC=Special Supplementary Program for Women, Infants, and Children.

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 of Body Mass Index (BMI) Z-score for Toddlers, measured over Baseline to 12-month Follow-up.

The primary endpoint is change in BMI z-score for toddlers from baseline to 12-month follow-up. Weight and height measurements were converted to age- and gender-specific BMI z-scores. Standardizing BMI for age and gender gives a measure intended to express a toddler’s BMI in relation to those characteristics, rather than relying on raw BMI alone.

The registry describes the BMI z-score range as usually between -5 and +5. It defines a score lower than -1.645 as underweight, scores from -1.645 to 1.036 as normal weight, and a score greater than or equal to 1.645 as obese. Those categories give context to the scale, but the primary endpoint is change in the continuous z-score, not simply a count of toddlers in each category.

A mean change can describe the group’s average movement on the scale, while the standard error describes the uncertainty in that estimated mean. A group average does not show how much individual toddlers varied, and a change in the average alone does not indicate how many children crossed a category boundary. The registry record does not report the endpoint values or a between-group estimate, so the direction, magnitude, and precision of the primary result are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record identifies a continuous primary outcome summarized as a mean with standard error. These terms describe different features of an estimate. A mean is an average on the outcome scale. A standard error describes how much an estimated mean would tend to vary across repeated samples under a statistical model. It is not the same as the standard deviation, which describes variation among individual observations. Neither the mean nor the standard error for the primary endpoint is reported in the registry record.

What does a mean change represent?

A change score compares measurements at two time points for the same outcome. In this study, the stated period runs from baseline to 12-month follow-up. A group mean change would describe the average change in BMI z-score among participants included in that analysis. To compare groups, an analysis would generally estimate a contrast between their changes or otherwise account for measurements over time. The registry record does not specify which approach was used, and no single comparison is posted.

Change scores and follow-up values answer related but distinct questions. A change score reflects movement from baseline; a follow-up comparison may also account for baseline values in a model. A baseline-adjusted model can be useful in randomized studies, but the registry record does not state whether such a model was used. It would not be appropriate to infer the analysis method from the endpoint label alone.

What does the standard error tell readers?

In general, a standard error describes uncertainty about an estimated quantity, such as a group mean. It does not describe the spread of individual toddlers’ BMI z-scores. A confidence interval uses an estimate and its uncertainty to express a range of values reasonably compatible with the data and the method used. A p-value addresses compatibility between data and a specified null hypothesis under an analysis model; it does not measure the size or practical importance of an effect. No confidence interval or p-value for a single primary comparison is reported in the registry record.

Statistical interpretation would depend on the between-group estimate as well as its uncertainty and the outcome scale. A small standard error would indicate greater precision for the estimate, while a large standard error would indicate less precision, in general. Neither can be assessed because the primary numerical results are not reported. A mean change by itself would also not reveal the distribution of individual changes or whether changes differed across subgroups.

Why can over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. It can make standard errors too small if a model’s variance assumptions are not appropriate, which can in turn make confidence intervals too narrow and tests appear more decisive than warranted. This concept is most often discussed for particular outcome models, such as counts, rather than as an automatic feature of a continuous mean outcome. The registry record does not report an over-dispersion assessment or a model for the primary endpoint, so no claim about it can be made for this trial.

What can the planning assumptions establish?

The record describes planning illustrations based on the observed effect, not the trial’s own design. They assume a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is described as a stated fraction of the observed effect. These are assumptions used for an illustration; they do not establish the actual allocation ratio, show that the trial was designed around that effect, or demonstrate power based on observed results. Sample sizes from planning illustrations are not observed power.

The registry record does not report a sample-size justification, the effect size used when planning the trial, or whether the study’s enrollment target was based on a particular endpoint. The planning assumptions should therefore be interpreted as separate from the trial protocol and from any inference about its primary result. The registry’s note that the primary outcome was not reduced to one comparison also means that a reader cannot match an illustration to a unique posted primary contrast.

Randomization can support a fair comparison by balancing prognostic factors on average, but it does not guarantee that every baseline characteristic is identical across groups. Masking can reduce some forms of bias, but this record does not describe which parties were masked or how. Neither design label reveals how the endpoint was analyzed, how missing data were handled, or whether analyses followed the originally assigned groups. Those details are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 7 outcome measures and 14 analyses, alongside a primary outcome and several secondary outcomes. Multiple outcomes, time points, or comparisons create a multiplicity issue: the more statistical questions that are tested, the greater the chance of obtaining at least one apparently notable finding by chance if no adjustment or prespecified interpretation is used. This is a general statistical concern, not a claim that the study’s analyses were invalid.

The record does not report whether investigators adjusted for multiple comparisons, designated a hierarchy among secondary outcomes, or prespecified which arm contrasts would be primary. The stated primary outcome was not reduced to a single comparison in the registry results. A multiplicity strategy and the complete analysis plan are not reported in the registry record, so readers cannot determine how the analyses were intended to control or interpret multiple testing.

Missing outcome data can affect both the precision and the validity of estimates, particularly if participants with missing measurements differ from those measured. The enrollment figure does not establish how many toddlers contributed baseline and 12-month measurements. The amount and pattern of missing data, reasons for missingness, and any imputation or sensitivity analyses are not reported in the registry record.

The analysis population is also not reported in the registry record. It is therefore unclear whether the posted analyses, if any, included all randomized participants, only participants with observed outcomes, or another population. The record does not state whether participants were analyzed according to their original randomized group or how departures from assigned intervention were handled. These omissions limit assessment of both the completeness and the interpretability of the efficacy analyses.

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 serious adverse event entries list 0 affected participants in each of the Maternal Lifestyle (Physical Activity and Nutrition), Responsive Parenting, and Child Safety groups. The deaths entry is 0 for each group. The listed counts at risk for serious adverse events are 94, 92, and 91, respectively. These are the figures recorded for the safety reporting period; the registry record does not give additional timing or event detail.

The other adverse event entries also list 0 affected participants in each group, with counts at risk of 94, 92, and 91, respectively. The list of top serious adverse event terms is empty. The zero entries mean no affected participants are listed in these registry fields; they do not establish that no event of any kind occurred outside the reporting definitions or period.

Counts at risk are the denominators associated with the safety entries, not necessarily the number enrolled or the number analyzed for the primary outcome. The registry record does not describe the event definitions, collection procedures, severity grading, or detailed follow-up window. These safety entries should therefore be read as the reported registry counts, not as a complete account of all possible harms or as an efficacy result.

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

The record documents a randomized, parallel comparison of two behavioral approaches with a child-safety attention control in toddlers from low-income families. It identifies change in BMI z-score from baseline to 12-month follow-up as the primary endpoint and lists diet quality, physical activity, and feeding style among secondary outcomes. Those details clarify the questions the study was designed to address.

The record does not, however, provide a single primary comparison or its numerical estimate. It therefore does not show whether BMI z-score changed, which group had the larger change, or how precise a between-group estimate would be. The stated hypothesis cannot be treated as a finding. The registry’s description of outcome categories and its list of secondary measures do not supply the missing outcome results.

This does not establish that the interventions had no effect; it means the registry record does not report results from which the effect can be evaluated. Nor does the enrollment count alone establish how many participants contributed outcome data. The available safety entries list zero affected participants in each group, but their scope and reporting details are not described sufficiently to treat them as a complete assessment of all adverse experiences.

The study can be characterized as a completed randomized trial with defined intervention content and a specified follow-up endpoint. Assessing its statistical findings requires the outcome estimates, uncertainty measures, analysis populations, missing-data information, and analysis methods. Those details are not reported in the registry record. Until they are available, claims about the size, direction, precision, or practical importance of any primary or secondary effect are not supported by this record.

13. Why This Trial Matters Statistically

This trial raises an important statistical distinction between a clearly named outcome and a result that can be interpreted. The record defines an age- and gender-specific BMI z-score and specifies a change period from baseline to 12-month follow-up. Yet it does not reduce the primary outcome to a single comparison or report a numerical estimate for one. A carefully defined endpoint is essential, but it cannot by itself answer whether randomized groups differed.

The design also illustrates why comparator details matter. Child Safety was an attention control involving safety-focused intervention for parents, rather than a no-contact group. The other arms addressed maternal lifestyle or toddler parenting. Understanding those intervention contents helps frame the contrast, while the absence of reported estimates prevents a statistical judgment about the contrasts themselves.

The record lists multiple outcomes and analyses, making transparency about prespecification and multiplicity relevant. Without the analysis plan, readers cannot tell which comparisons were prioritized or how findings across outcomes were intended to be interpreted. Similarly, enrollment does not reveal how many participants had follow-up measurements, so reporting analysis populations and missing-data handling would be important for evaluating precision and potential bias.

Finally, planning illustrations should be separated from trial results. Assumptions such as equal allocation between two arms, a two-sided significance level of 0.05, and a normal approximation can be useful for illustrating sample-size implications, but they are not evidence about observed effects or the trial’s original planning. The record’s limitations make statistical transparency—not a conclusion about the intervention—the central lesson.

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 statistical interpretation is that the primary endpoint is not reported as a single comparison. The registry record does not include a mean change, between-group estimate, confidence interval, or p-value for that comparison. Consequently, the effect’s direction, magnitude, and precision cannot be assessed from the record.

The record does not describe the statistical model, adjustment for baseline measurements, or the specific contrasts used. It lists 14 analyses but does not provide a complete analysis plan or explain how multiplicity was addressed. The information needed to understand the analysis population, adherence to randomized assignment, and treatment of missing follow-up data is also not reported in the registry record.

The registry labels the study double-masked but does not identify who was masked or how masking worked. It classifies the study as randomized and parallel, but does not report the randomization procedure, allocation ratio, or related implementation details. These gaps prevent a full assessment of how the design was carried through in practice.

The safety entries list zero affected participants for serious and other adverse events, but the registry record does not describe event definitions, collection methods, or detailed reporting periods. The recorded counts at risk should not be assumed to be the efficacy analysis denominators. Finally, the population is defined as WIC-eligible toddlers in low-income families; the record alone does not establish how results would apply to other populations. In this case, the lack of a reported primary result also prevents assessing applicability based on the size or precision of an observed effect.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Toddler Overweight Prevention Study Among Low-Income Families — NCT02615158.
• Registry record last updated 2020-05-12; status last verified 2020-05.
• Results first posted 2020-05-12.
• 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

NCT02615158 is listed as a completed randomized, double-masked, parallel behavioral study with enrollment of 277. Its groups were Maternal Physical Activity and Nutrition, Parenting, and Child Safety. The stated primary outcome was change in toddler BMI z-score from baseline to 12-month follow-up, summarized as a mean with standard error.

The registry describes the population as toddlers in low-income families, defined as WIC-eligible, with income < 185% of the poverty index. It lists secondary outcomes concerning diet quality, physical activity, and feeding style. The primary outcome was not reduced to a single comparison, and a numerical primary result is not reported in the registry record. Safety entries list zero affected participants and zero deaths in each group.