For Exercises 19–22, do the following:

  1. Provide the null and alternative hypotheses.
  2. Explain what it would mean to make a Type I error.
  3. Explain what it would mean to make a Type II error.

Question 9.19

19. A psychologist wants to determine whether the mean achievement gap has decreased from its previous level of 10 points.

9.1.19

(a) versus (b) Conclude that the population mean achievement gap has decreased when, in reality, it has remained the same. (c) Conclude that the population mean achievement gap has remained the same when, in reality, it has decreased.