In answering the following exercises, it will be helpful to have before you the definitions of Type I and Type II errors that you have already learned. Here is a reminder:

Type I: There really is not an effect (population truth), but you find one (your decision) in your study.

Type II: There really is an effect (population truth), but you don’t find one (your decision) in your study.

Two fishermen, Abe and Gabe, are debating the relative merits of two lakes for fishing. Based on their experience in fishing in the two lakes, they decide that the two lakes are equivalent in terms of the number of fish. A researcher overhears their conversation and decides to test their conclusion. Using advanced sonar sensing, she counts the actual number of fish in each lake. She finds that one lake has many more fish than the other lake does. Assuming that her findings reflect the population truth about the two lakes, what type of error did Abe and Gabe make in their judgment—was it Type I or Type II? Explain your answer.