Mediation might be the ultimate example of how a method continues to be used despite a vast number of papers and textbooks describing the extremely strong assumptions required to estimate unbiased effects. My aim with this post is not to show some fancy method that could help reduce bias; rather I just want to present a small simulation-based example of the underappreciated consequences of measurement error and confounding. There’s been many other people making the same point, for instance, Dunn & Bentall (2007) expressed some strong concerns about investigating mediators in …