Randomization and masking
WBOTs
CHWs and the dyads they served were randomized at the level of WBOT (cluster) to either the intervention or control group by a member of the investigator team (PCR). The randomization was performed prior to the start of CHW training and only CHWs in the intervention arm were trained on the study job aid. In 2 instances where more than 1 WBOT operated out of the same health facility, WBOTs were grouped together in the same study cluster to reduce the risk of contamination. Cluster assignment was determined using a covariate constrained randomization procedure that maximized balance on number of health facilities, average monthly volume of under-5 consultations at health facilities over the past year, number of WBOTs, number of CHWs, average CHW age, education, and years in the position. As part of an exploratory aim that is outside the scope of this paper, intervention WBOTs were then randomized a second time using the same covariate constrained randomization procedure to receive one of 2 versions of the CHW job aid, which differed only with respect to the suggested play-based activities. Group assignment was masked from all data collectors, but masking of participating CHWs and dyads was not possible.