Why would we ever want to calculate power after an experiment has been run, as we just did in Exercises 15.22 and 15.23?

Exercise 15.22

Calculate the power of the anorexia experiment in Section 14.1, assuming that the parameters have been estimated correctly.

Exercise 15.23

Use G*Power or Piface (Lenth’s program) to calculate the power of the comparison of Thematic Apperception T scores from the parents of schizophrenic and normal subjects in Exercise 14.8.

Exercise 14.8

The Thematic Apperception Test (TAT) presents participants with ambiguous pictures and asks them to tell a story about them. These stories can be scored in any number of ways. Werner, Stabenau, and Pollin (1970) asked mothers of 20 Normal and 20 Schizophrenic children to complete the TAT and then scored for the number of stories (out of 10) that exhibited a positive parent–child relationship. The data follow:

Transcribed Image Text:

Normal Schizophrenic 2 1 Normal Schizophrenic 0 2 4 8 4 6 3 1 4 4 6 4 2 1 3 2 72131 2 11 4 3 3 2 63 4 2 3 3 0 1 2 2