In terms of case variety, Gary King, Robert Keohane, and Sidney Verba alert from "deciding on to the dependent variable". They argue one example is that scientists are not able to make valid causal inferences about war outbreaks by only thinking about instances in which war did transpire (the researcher https://holdensrtph.blogzet.com/5-tips-about-case-solution-you-can-use-today-46988920