A few days ago, I came back on a sentence I found (in a French newspaper), where someone was claiming that “… an old variable explains 85% of the change in a new variable. So we can talk about causality” and I tried to explain that it was just stupid : if we consider the regression of the temperature on day against the number of cyclist on day , the exceeds 80%… but it is hard to claim that the number of cyclists on … Continue reading Testing for a causal …