Imagine you have 20 experiments, each with a 5% chance that the null hypothesis shows a positive result, then there is a good chance that one of them will be po

Imagine you have 20 experiments, each with a 5% chance that the null hypothesis shows a positive result, then there is a good chance that one of them will be positive even if null is true for all of them. That experiment is bunk but you say p=0.05 so all is good!