8a.) A type I error occurs when an investigator rejects a null hypothesis that is actually true in the population. A type II error occurs when an investigator accepts a null hypothesis that is not actually true in population. 8b.) Type I error: the recent winners appear to be thinner than those from the 1920s and 1930s even though there is no difference in the BMI. Type II error: there appears to be no difference in the BMI between the recent winners and those from the 1920s and 1930s even though the recent winners are thinner than those from the 1920s and 1930s