Multisample analyses
Multisample analyses permitted for tests of difference in parameter estimates for each model across the Australian and U.S. samples. For the model excluding past behavior (Model 1), only effects of intention on habit at baseline, habit at follow-up on social distancing behavior, and intention on action planning differed across samples. These effects were significantly larger in the U.S. sample. Some effects with observed differences across samples, such as the effect of habit at baseline on intention or the moderator effect of planning on the intention–behavior relationship, did not differ significantly across samples. For the model including effects of past behavior (Model 2), multisample analysis revealed no differences in effect size across samples, indicating that the attenuating effect of past behavior on model effects also had the effect of eliminating the few differences in model effects across samples. Full details of the multiple-group analysis are presented in Supplementary Appendix G.