1. Figure A1. Concordance and discordance of rejection regions of heterogeneity tests of odds ratio (OR) and odds ratio differences (ORD) when there is no interaction on either scale, by type of ORD heterogeneity test, sample size and second exposure odds ratio. OR heterogeneity was assessed by using a multiplicative interaction term from a logistic regression model; ORD heterogeneity was assessed by using either the interaction term from an additive relative risk regression model (AddRR); the relative excess risk due to interaction (RERI), the synergy index (SI), or the proportion of interaction attributable to the joint exposure to two risk factors (APAB). When two exposures do not interact on either the additive or multiplicative scale, one exposure-odds ratio is necessarily equal to one. Results are averaged over exposure prevalence. (Note: Figure prints better on a color printer.)