Moderation by race was assessed by creating an interaction term and testing its significance in the multivariable model.
Statistical analysis was performed by testing the interaction between sex and time for the time points t2-t4.
We analyzed the trend by testing for interaction of the social factor and survey year in a dataset pooled from all three surveys.
The moderation effect of puberty was examined by testing the interaction between time and puberty level.
The assumption of proportional hazards was evaluated by testing for interaction with a continuous time variable.
We tested the proportional hazards assumption by testing an interaction of each variable with log of time.
Proportional hazards assumptions were verified by testing the interaction with time using the likelihood ratio test (P = 0.27).
We assessed the proportional hazards assumption by testing the interaction terms of the factors listed in Table 2 with time.
Homogeneity of slopes was assessed graphically and by testing the interaction term treatment*PTA_T1 in a preliminary model.
The assumption of homogeneous regression slopes was examined by testing the interaction between diagnosis group and age.
We compared the magnitude of association across groups by testing the interaction between genetic relatedness and breastfeeding.
