10.23 State the null hypothesis, Ho, and the alternative hypothesis, Ha, that would be used to test these claims:

a. There is an increase in the mean difference between posttest and pretest scores.

b. Following a special training session, it is believed that the mean of the difference in performance scores will not be zero.

c. On average, there is no difference between the readings from two inspectors on each of the selected parts.

d. The mean of the differences between pre–selfesteem and post–self-esteem scores showed improvement after involvement in a college learning community.