With regard to case collection, Gary King, Robert Keohane, and Sidney Verba warn against "selecting to the dependent variable". They argue for instance that scientists can't make valid causal inferences about war outbreaks by only investigating circumstances in which war did occur (the researcher also needs to examine cases https://reidjuzyp.ssnblog.com/32603341/buy-case-solution-can-be-fun-for-anyone