Stratified model for growth spurt rate. Results from 100 repeated holdouts testing the association between the phthalate index and rate of first growth spurt, controlling for sex, SGA, NICU morbidity score, and year of birth, and including stratified weights only (N=96; training n~38, validation n~58). A. shows the distribution of WQS estimates where data points represent the estimate for each holdout and the closed diamond shows the mean effect estimate and the boxplot shows the 25th, 50th, and 75th percentiles and the whiskers show the 2.5th and 97.5th percentiles. B. shows the relative weight of each phthalate metabolite, using the average weight from the 100 holdouts divided by the sum of the averages, stratified by sex.