If a researcher rejects a null hypothesis when that hypothesis is actually true, he has committed: a type I error a type II error a type III error no error a type I error a type II error a type III error no error Solution If a researcher rejects a null hypothesis when that hypothesis is actually true, he has committed: a type I error a type II error a type III error no error A type I error is the incorrectly rejecting a true null hypothesis. a type I error a type II error a type III error no error.