We also sought to confirm that our results persisted to other operationalizations of child CP, as G × E modeling results can be influenced by the scaling and distribution of the outcome variable (Purcell, 2002). This re-analysis was conducted in two ways. First, rather than log-transforming our CP variable to adjust for positive skew, we instead rank-normalized and Blom-transformed CP separately by sex (skew after this transformation was 0.30). Our primary G × E analyses were then re-run using the Blom-transformed CP variable as our outcome. Second, we created a second measure of CP, in which the maximum CP score according to any one informant was used as an index of child CP. Analyses were then re-run using ‘maximum CP’ as our outcome variable.
