相互作用の探索：相互作用研究のための理論的および方法論的フレームワーク

We suggest that psychological research into interaction effects might benefit from analyzing potential interactions from the perspective of the Positive Predictive Value (PPV). The PPV denotes the post-study probability that a claimed effect is true, based on the pre-study probability that said effect exists, the power of the respective test and the significance level used for testing. We use the PPV in order to propose a framework structuring potential interaction effects based on their (theoretical) plausibility and their shape. Specifically, the position of a hypothesized interaction in the proposed framework may inform sample-size planning and the choice of alpha levels prior to a study; and it may inform confidence into results after a study. Finally, we present a heuristic approach for planning research on interactions based on R (the pre-study probability that an effect exists), the PPV (the post-study probability that a claimed effect is true) and α (the significance level used for significance testing). In doing so, we aim to provide a nuanced view on the feasibility of investigating into interactional hypotheses, a view that is critical where needed but that at the same time does not discourage research on interactions.