Brief Intervention in At-Risk First-time Mothers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Brief Intervention in At-Risk First-time Mothers (NCT00230009), a randomized phase 1, phase 2 study. The primary outcome is Alcohol Use.

2. Clinical Question

3. Trial Design

The registry record describes a randomized, single-masked, parallel-group study in Phase 1 and Phase 2. The listed enrollment is 100, and the trial status is completed. The record gives a start date of 2004-04 and primary completion of 2007-03. Wayne State University is listed as the sponsor. Substance Use is the listed condition. These registry entries identify the registered design and administrative record; they do not supply details about how randomization was generated, how allocation was concealed, or which people were masked. Those details are not reported in the registry record.

The two groups were Assessment Only and Brief Intervention Session. The intervention is classified as behavioral and named Brief motivational intervention. The registry record gives no arm-specific procedural description beyond the arm names. Its summary describes a preliminary controlled trial intended to address child maltreatment risk among low-income pregnant mothers. Risk-factor foci included substance abuse, social isolation, depression, violence exposure, and maladaptive child-rearing attitudes or beliefs. These are descriptions of the study rationale and intervention focus, not evidence that each factor was measured as an outcome.

The primary outcome is alcohol use at 3 month follow-up. The posted analysis includes 19 participants in Assessment Only and 24 in Brief Intervention Session. The registry record states that 43 participants returned for follow-up and were the only participants analyzed for this outcome. This follow-up population is narrower than the listed enrollment, so the primary results describe those with outcome data rather than every person enrolled. The record does not explain the reasons for non-return or provide a comparison of participants with and without follow-up data.

Depression is listed as a secondary outcome, and one secondary outcome is posted. The registry record lists five outcome measures overall but does not post analyses for the secondary outcome. It also lists no reported analyses. This means the posted numerical comparisons can be described, but the original prespecified analysis plan, handling of missing data, and any model adjustments are not reported in the registry record. The design information establishes the broad randomized comparison, while leaving important implementation and analysis details unknown.

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.

Single Session Intervention/Control

Follow-up

Analysis population for the primary outcome, as defined in the registry: A total of 43 participants returned for follow-up and were the only participants analyzed on this outcome.

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 Alcohol Use, measured over 3 month follow-up.

The primary endpoint is the mean score for alcohol-use frequency at the 3 month follow-up. The registry description says frequency of use in the past 30 days was measured using the Alcohol Use Disorders Identification Test (AUDIT). The reported score ranged from 0 to 5 in the follow-up sample; higher scores indicate more frequent substance use. The outcome is continuous, and the registry reports a group mean and standard deviation for each arm.

A mean provides a measure of the average score in each group, while the standard deviation describes the spread of individual scores around that group’s mean. Reporting both helps distinguish the location of the group average from the variability among participants. The mean difference compares the group averages on the same scale, with the contrast defined as Brief Intervention Session relative to Assessment Only. A negative difference therefore corresponds to a lower observed average in the intervention group.

Alcohol use is relevant to the trial’s stated focus on child maltreatment risk factors because the registry summary explicitly includes substance abuse among the areas of concern. That rationale does not make the alcohol score a direct measure of child maltreatment, nor does the endpoint alone represent every intervention target. The endpoint captures one reported dimension of risk at follow-up. The registry record does not report the original rationale for choosing this outcome as primary or provide additional detail about the measure’s scoring beyond the range and direction described.

7. Results Posted in the Registry

• Brief Intervention Session: mean 0.92 versus 1.37 on control; difference -0.45 (95% CI -1.34 to 0.44), standardized effect d = -0.31; z-test p = 0.321.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Depression

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Brief Intervention Session: mean 20.33 versus 19.74 on control; difference 0.59 (95% CI -3.22 to 4.40), standardized effect d = 0.09; z-test p = 0.762.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Brief Intervention Session and the control. The interval gives the range of effects that remain compatible with the data.

The posted secondary outcome is depression at the 3 month follow-up. Its observed mean difference is small relative to its uncertainty, and its interval also includes zero. The direction of the raw difference is opposite to the primary alcohol-use contrast: the intervention group’s depression mean is higher, whereas its alcohol-use mean is lower. Taken together, the posted results do not form a consistent pattern of lower average scores across both reported outcomes. Neither outcome’s unadjusted comparison clearly separates from zero.

The secondary result should be interpreted alongside, not as confirmation of, the primary result. Both are follow-up comparisons among the participants with reported outcome data, and both are unadjusted recalculations. They concern different constructs and scales, so the numeric magnitudes cannot be compared directly. A difference in direction across outcomes does not by itself establish a trade-off or a relationship between depression and alcohol use; the record does not report an analysis of such a relationship.

Unadjusted secondary results generally carry less weight than a prespecified primary analysis because multiple outcomes create more opportunities for apparently notable findings, even when there is no reliable underlying difference. This is a general statistical concern, not a claim that a particular adjustment was required or performed in this trial. The registry record lists five outcome measures overall, identifies depression as a secondary outcome, and reports no analyses for that secondary outcome. It does not describe a multiplicity strategy, a hierarchy for outcomes, or which outcomes were prespecified for inferential testing.

The broader reading is therefore cautious: the posted secondary comparison does not strengthen the primary finding into a general pattern across outcomes. At the same time, the absence of a clear result should not be treated as proof of no difference. The secondary outcome has its own uncertainty, and its interpretation is limited by the available follow-up data and the lack of reported analysis-plan detail. The registry record does not report other secondary endpoint estimates, so no broader claim across all outcome measures can be made.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Depression

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: each participant has a score, and the registry reports the mean and standard deviation within each group. The mean difference is a direct contrast between group averages on the original scale. For the primary outcome, the reported contrast is Brief Intervention Session minus Assessment Only. Its negative sign indicates that the intervention group’s observed mean is lower. The contrast is easier to interpret in the outcome’s original units than a standardized effect, although it does not describe every participant’s experience.

What does the standard deviation describe?

A standard deviation describes how dispersed scores are within a group. It is not the same quantity as the standard error. The standard deviation characterizes variation among participants, while the standard error characterizes uncertainty in an estimated statistic, such as a group mean. The posted standard deviations are 1.57 for Assessment Only and 1.35 for Brief Intervention Session. The displayed standard errors for those means are 0.360 and 0.276, respectively. These measures answer different questions: a group can have considerable participant-level variation while its estimated mean has a different degree of precision, depending in part on the amount of outcome information.

How should the mean difference be read?

The unadjusted mean difference is -0.45. Since higher scores indicate more frequent use, the negative sign indicates a lower observed average in the intervention group than in Assessment Only. The difference remains expressed in the score’s original units. It does not mean that every person in the intervention group scored lower, and it does not describe a change from baseline: the registry reports a follow-up comparison, not a baseline-to-follow-up contrast. The record does not report a baseline alcohol-use result for this endpoint.

What does a confidence interval contribute?

A confidence interval gives a range of values compatible with the observed data and the calculation’s assumptions. It communicates uncertainty about the estimated contrast rather than just reporting one point estimate. For the primary contrast, the interval runs from -1.339 to 0.439. The range includes zero and also includes negative and positive values. In general statistical terms, an interval that includes zero does not clearly distinguish the observed contrast from no difference at the chosen inferential standard. The registry record does not report the confidence level or the original interval-construction method, so the interval is interpreted as posted without attributing an unreported procedure to the trial.

What does the p-value say?

The reported p-value is unadjusted and equals 0.321. In general, a p-value measures the compatibility of data with a null hypothesis under a specified statistical model. It is not the probability that the null hypothesis is true, and it is not a measure of the clinical importance of an estimate. The registry record does not report the sponsor’s test procedure, so this value should be understood as the unadjusted result in the posted recalculation rather than as a description of a confirmed original analysis.

Why are standardized effects also useful?

A standardized effect expresses a mean contrast relative to the variability of the outcome, which can help compare effects measured on different scales. The posted pooled standard deviation for the primary outcome is 1.451, and the standardized difference is -0.310 when rounded to no more than three decimal places. Standardization has a cost: it is less directly interpretable in the AUDIT frequency score’s units, and it depends on the variability estimate. It does not remove uncertainty or correct for incomplete follow-up.

What does over-dispersion mean in general?

Over-dispersion is a general issue for some statistical models when observed variability is greater than the model assumes. It can make standard errors too small if the model fails to account for the extra variation. The primary endpoint is summarized as a continuous mean with standard deviation, and the registry record does not report an over-dispersion analysis. Therefore, over-dispersion should not be presented as a finding about this trial. It is a general reminder that inferential precision depends on whether a model’s assumptions adequately describe the observed data.

What is and is not known about the calculation?

The mean differences and related statistics are simple unadjusted recalculations from the posted summary statistics. The registry record does not report a statistical analysis plan, adjustment covariates, a test specification, or a method for handling missing outcomes. The sample-size illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation, but these are planning assumptions for the illustrations, not reported assumptions for the trial’s original design. The distinction matters: the planning calculation answers a prospective question about the participant numbers that might be needed under stated assumptions, whereas the outcome comparison describes the observed follow-up data.

11. Confidence Intervals and Precision

The primary mean difference is -0.45, with an interval from -1.339 to 0.439. The interval is wider than the point estimate and extends across zero. That breadth means the observed data do not pin down the size or direction of the underlying contrast precisely. Values favoring a lower average in Brief Intervention Session and values favoring a higher average are both within the displayed range. The interval is not evidence that every value in the range is equally plausible; it is a way of expressing uncertainty under the calculation’s assumptions.

Precision is limited in part because the outcome analysis includes only participants who returned for follow-up: 19 in Assessment Only and 24 in Brief Intervention Session. Those arm sizes are the outcome-specific analysis counts, while listed enrollment is 100. The registry record does not report why some participants did not return, whether the chance of follow-up differed by group, or whether missing outcome data were addressed by an analysis beyond the observed cases. These unknowns affect how confidently the follow-up contrast can be extended to the enrolled population.

The p-value of 0.321 is consistent with the interval’s failure to distinguish the observed contrast clearly from zero. Neither the p-value nor the interval establishes equivalence or absence of an effect. The point estimate is a useful summary of the observed group separation, but the uncertainty around it is substantial. The record does not report a confidence level or original interval method, so those details should not be inferred. The results support a cautious description of a lower observed mean in the intervention group, accompanied by considerable uncertainty about the underlying difference.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. They are based on a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each row uses the stated fraction of the observed effect as the effect to detect. The original trial’s own sample-size assumptions and justification are not reported in the registry record, so these figures should be read only as planning illustrations based on the observed contrast, not as a reconstruction of the trial’s design.

The 80% power column gives the participants per arm estimated to yield an 80% chance of detecting the specified effect under those planning assumptions, if that effect and the assumptions were correct. The 90% power column gives the corresponding per-arm number for a higher target chance of detection. For the full observed effect, the illustrations give 164 participants per arm for 80% power and 219 for 90% power. Planning for 75% of the observed effect gives 291 per arm for 80% power and 389 for 90% power. Planning for 50% of the observed effect gives 653 per arm for 80% power and 874 for 90% power.

Smaller effects are harder to distinguish from random variation, so they require more participants under the same assumptions. The increasing figures across the rows illustrate that relationship. These calculations are not observed power: they do not describe the probability that the completed trial detected its true effect, and they do not establish what effect the trial actually had. They are prospective illustrations, not evidence about outcome efficacy or about the original enrollment rationale.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -0.450; pooled standard deviation σ = 1.451.
2. n = 2 × (1.96 + 0.842)² × 1.451² / -0.450² = 163.1, rounded up to 164 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -0.45                      # observed difference in means
sigma <- 1.45069957892483                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(230009)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 164 (80% power), 219 (90% power)
 75% of observed effect: n per arm = 291 (80% power), 389 (90% power)
 50% of observed effect: n per arm = 653 (80% power), 874 (90% power)
power.t.test: 164.1 
Simulated power at n = 164 per arm: 0.802 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when several outcomes or statistical comparisons are examined. In general, the more tests considered, the greater the chance that at least one result will look unusual by chance alone. The registry record lists five outcome measures and names depression as a secondary outcome, but it does not report a multiplicity adjustment, an outcome hierarchy, or a prespecified plan describing how findings across outcomes would be interpreted. The number of posted outcome measures is not the same as the number of statistical tests actually conducted; the registry record lists no reported analyses. It is therefore not possible to determine from the record how multiplicity was handled in the trial’s own analysis.

The primary alcohol-use comparison and the posted depression comparison are unadjusted recalculations from summary statistics. Their p-values should not be treated as if they had been adjusted for testing several outcomes. They are also not enough to determine whether the trial’s original analysis considered other outcomes, subgroups, or repeated measures. Those details are not reported in the registry record. The number of reported analyses is listed as zero, so the posted estimates should not be mistaken for a complete account of the trial’s statistical analyses.

Missing outcome data are a separate concern. Although listed enrollment is 100, the primary outcome analysis includes the participants who returned for follow-up, and the registry record states that only those participants were analyzed on that outcome. The record does not report why other enrolled participants did not contribute to the follow-up result, the amount or pattern of missingness for each arm beyond the outcome-specific analysis counts, or whether any imputation, weighting, or sensitivity analysis was used. It also does not describe an intention-to-treat analysis population.

When follow-up participation is related to outcome values or group assignment, an analysis limited to observed outcomes can differ from the comparison that would have been obtained with complete follow-up. This is a general possibility, not evidence that such bias occurred in this trial. Randomized assignment supports the initial group comparison, but it does not itself resolve selection after randomization. Without the reasons for missingness and the analysis plan, the degree to which the observed follow-up groups represent the randomized groups remains uncertain.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The registry record reports serious adverse event counts for the two named groups. For Assessment Only, 50 participants are listed as at risk and 0 as affected by serious adverse events. For Brief Intervention Session, 50 are listed as at risk and 0 as affected. Other adverse events are also reported as 0 affected in each group, with 50 at risk in each. No serious adverse event terms are listed.

These entries describe what is recorded in the safety fields. They do not establish that no adverse experiences of any kind occurred, because the record distinguishes serious events from other events and supplies no narrative detail or event terms. Deaths are not reported in the registry record. The safety figures should not be combined with the follow-up outcome counts: the record gives different safety and efficacy denominators, and does not explain their relationship. The entries are descriptive counts, not a comparative safety analysis. With no affected events recorded, the registry data do not provide an estimate of relative event risk or a precise assessment of uncommon harms.

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

The posted results show that the observed mean alcohol-use score at the 3 month follow-up was lower in Brief Intervention Session than in Assessment Only. The unadjusted difference is -0.45 on the reported score scale. The interval extends across zero, and the unadjusted p-value is 0.321. The appropriate statistical conclusion is that the observed contrast is uncertain: the data do not clearly distinguish a difference from no difference, and they do not establish the direction or size of any underlying effect with precision.

That conclusion is narrower than saying the intervention did or did not work. The primary endpoint is a follow-up measure of alcohol-use frequency, not a direct measurement of child maltreatment. The registry summary describes a broader intervention rationale, including multiple risk factors, but the posted primary result addresses only the alcohol-use endpoint. It cannot stand in for every intended intervention target or for child maltreatment outcomes that are not reported as the primary endpoint.

The analysis is based on the participants who returned for follow-up. The record does not explain why others did not contribute outcome data or report a missing-data analysis. The group comparison is unadjusted, and the original statistical plan is not reported. These limitations prevent a confident extension from the observed follow-up sample to all enrolled participants or to a broader population.

The result is also not evidence that the groups are equivalent. Showing that an interval includes zero is not the same as demonstrating that any difference is sufficiently small to be unimportant. The record does not state an equivalence margin or a non-inferiority objective. The clearest interpretation is therefore restrained: the observed follow-up means differ in the stated direction, while uncertainty is too substantial for a firm conclusion about an underlying group difference. The posted data do not settle the intervention’s effect on alcohol use or on child maltreatment risk.

17. Why This Trial Matters Statistically

This trial illustrates why an estimated effect and its precision need to be read together. The point estimate for the primary endpoint is a straightforward group contrast, but its interval covers values on either side of zero. Reporting only the group means or only the p-value would conceal important parts of that interpretation. A statistical result can point in one direction while still leaving considerable uncertainty about the true size and direction of the contrast.

The registry record also makes the analysis population visible: the primary result concerns participants who returned for follow-up. That detail matters because randomization describes assignment at the start of a trial, while the posted outcome comparison is based on follow-up data. When the record does not explain missing outcomes or the analysis population beyond observed follow-up, readers should distinguish the randomized design from the data actually used for the reported endpoint.

The study provides an example of how preliminary trials can produce estimates useful for planning without providing definitive evidence. The planning illustrations make explicit that assumptions about the effect to detect and desired power affect the participant numbers. They are not evidence that the original trial was designed using those assumptions, nor are they a substitute for a reported design justification.

Finally, the combination of a primary endpoint, a listed secondary outcome, multiple registered measures, and no reported analysis plan highlights the value of transparent outcome and multiplicity reporting. Without that context, readers cannot determine how the posted comparisons relate to all analyses that may have been planned or conducted. These are general lessons about statistical interpretation grounded in the features and omissions of this registry record.

18. 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 primary outcome is available only for participants who returned for follow-up. The registry record identifies that follow-up group as the analysis population but does not report reasons for missing outcomes, the outcome status of those not followed, or sensitivity analyses. This limits confidence in extending the observed contrast to all enrolled participants. The listed enrollment and the primary outcome analysis population should not be treated as interchangeable.

The outcome is a self-described frequency score measured at the 3 month follow-up, as characterized by the registry entry. The record reports the score range and direction but does not provide additional information about measurement properties, baseline values, or changes from baseline. The endpoint therefore supports a between-group comparison at follow-up, not an assessment of within-person change or persistence beyond that follow-up.

The comparison statistics are unadjusted recalculations from group summaries. No sponsor analysis is reported for the primary outcome, and the original test, confidence-interval method, covariate adjustments, and missing-data procedures are not reported in the registry record. The single-masked designation is recorded, but the identity of the masked party is not specified. Details of randomization generation and allocation concealment are also not reported.

The registry describes the study as preliminary and lists a broad intervention focus, while the posted primary result concerns alcohol-use frequency. No primary result for child maltreatment itself is presented in the registry record for this analysis. The record also does not give the intervention session’s detailed content or exposure, and it does not explain the role of the listed five outcome measures relative to the one posted secondary outcome. These gaps limit conclusions about implementation, completeness of reporting, and generalizability beyond the follow-up sample.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Brief Intervention in At-Risk First-time Mothers — NCT00230009.
• Registry record last updated 2013-08-08; status last verified 2013-08.
• Results first posted 2013-08-08.
• 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.

22. Record Summary

The registry record describes NCT00230009, Brief Intervention in At-Risk First-time Mothers, as a completed randomized, single-masked, parallel-group study in Phase 1 and Phase 2, sponsored by Wayne State University. Listed enrollment is 100, with a start date of 2004-04 and primary completion of 2007-03. The study compared Assessment Only with a Brief Intervention Session using a brief motivational behavioral intervention.

The primary outcome was alcohol-use frequency at the 3 month follow-up, measured with AUDIT and reported as a mean and standard deviation. The outcome analysis included participants who returned for follow-up. The observed intervention-group mean was lower, but the unadjusted difference interval included zero and the estimate was imprecise. Depression was listed as a secondary outcome. The registry record does not report the original statistical plan, missing-data procedures, or multiplicity strategy.