Bulimia study. The “fear of negative evaluation” (FNE)

scores for 11 female students known to suffer from the eating disorder bulimia and 14 female students with normal eating habits, first presented in Exercise 2.44 (p. 80), are reproduced in the next table. (Recall that the higher the score, the greater is the fear of a negative evaluation.)

Bulimic LO5 students: 21 13 10 20 25 19 16 21 24 13 14 Normal students: 13 6 16 13 8 19 23 18 11 19 7 10 15 20 Based on Randles, R. H. “On neutral responses (zeros) in the sign test and ties in the Wilcoxon-Mann-Whitney test.” The American Statistician, Vol. 55, No. 2, May 2001 (Figure 3).

a. Locate a 95% confidence interval for the difference between the population means of the FNE scores for bulimic and normal female students on the MINITAB printout shown on page 478. Interpret the result.

b. What assumptions are required for the interval of part a to be statistically valid? Are these assumptions reasonably satisfied? Explain.

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Two-Sample T-Test and CI: FNESCORE, GROUP Two-sample T for FNESCORE GROUP N Mean StDev SE Mean Bulimic 11 17.82 4.92 Normal 14 14.14 5.29 1.5 1.4 Difference mu (Bulimic) Estimate for difference: - mu (Normal) 3.68 95% CI for difference: (-0.60, 7.95) T-Test of difference = 0 (vs not =): T-Value = 1.78 P-Value 0.089 DF 23 Both use Pooled StDev = 5.1303