Statistical analyses
REGRESSION
Data summaries and analyses were performed for the total sample and then for the youth and adult subsamples separately. Time 2 and 3 proportions of UNAIDS knowledge were compared to baseline proportions using the McNemar’s test for paired binary data. Paired t-tests were employed to compare the mean HIV/PMTCT Knowledge Index at Times 2 and 3 to that of the baseline. To evaluate bivariate relationships between sociodemographic factors, which were all categorical variables, and the dichotomous UNAIDS Knowledge outcome at each time point, Chi-squared tests were employed. The relationships between sociodemographic factors and the HIV/PMTCT Knowledge Index were evaluated using t-tests for binary factors or analysis of variance models (ANOVA) for factors with more than two levels.In the multivariate analyses, intervention effectiveness was identified when the intervention group demonstrated significantly higher increasing trend in knowledge, and there were significant intervention-control differences at each of the follow-up time points, either in odds ratio for the binary UNAIDS Knowledge, or in mean differences for the HIV/PMTCT Knowledge Index. The magnitudes of the intervention effects over time were estimated using multivariate models for longitudinal design, controlling for baseline and time-varying sociodemographic factors. Specifically, generalized estimating equation (GEE) models were used to model the dichotomous UNAIDS Knowledge over time. Mixed-effects regression models (MRM) were used to model the repeatedly measured HIV/PMTCT Knowledge Index. Variance-covariance structures for repeated measures (in GEE) and random effects plus error structure (in MRM) were selected using fit statistics such as Akaike information criterion (AIC) and likelihood ratio tests when possible. Due to the stepped wedge design, in which all individuals were in the control group at baseline, group effect was not entered in the regression models as an additive fixed effect. Instead, group by time interaction terms, which indicated group differences in over-time trends, were the primary focus of inferences. For the total sample, significant fixed-effects sociodemographic factors, (baseline age group, self-identified sex,, education level, religious involvement) and the time-varying effect (partner status) were controlled after backward model selections in the longitudinal models. For the youth and adult subsample analyses, baseline age replaced age group and whether currently in school was added as a time-varying covariate for the Youth Subsample only. Covariates-adjusted time-point specific group differences and their 95% confidence interval estimates were reported for both knowledge measures (group odds ratios, ORs, for UNAIDS Knowledge and group mean differences for HIV/PMTCT Knowledge index). All statistical tests were 2-tailed, controlling for Type I error probability of 0.05. The statistical software program SAS 9.4 [