12. Exercise 2.7.8 uses Zung Anxiety Scale (ZAS) scores of 26 subjects with panic disorder who participated in a study conducted by Stein and Uhde (A-12). In their study these investigators also used 22 healthy control subjects (that is, subjects who did not have panic disorder). The following are the ZAS scores of 21 of these healthy controls:

26 28 34 26 25 26 26 30 34 28 25 26 31 25 25 25 25 28 25 25 25 SOURCE: Thomas W. Uhde, M.D. Used with permission.

a. Combine these scores with the scores for the 26 patients with panic disorder and construct a stem-and-leaf plot.

b. Based on the stem-and-leaf plot, what one word would you use to describe the nature of the data?

c. Why do you think the stem-and-leaf plot looks the way it does?

d. For the combined ZAS data, and using formulas for ungrouped data, compute the mean, median, variance, and standard deviation.