At week 24 , the Aberrant Behavior Checklist-Irritability subscale declined 47.7 % in parent training ( from 23.7 to 12.4 ) compared with 31.8 % for parent education ( 23.9 to 16.3 ) ( treatment effect , -3.9 ; 95 % CI , -6.2 to -1.7 ; P < .001 , standardized effect size = 0.62 ) .