In the article “Modification and evaluation of a velopharyngeal insufficiency quality-of-life instrument” published in JAMA Archives of Otolaryngology – Head and Neck Surgery (Skirko, et al., 2012), the authors reported the results of a twosample study of velopharyngeal insufficiency (VPI) quality of life with the quality of life instrument (VPIQL). The subjects in the study were 29 patients with VPI and 30 control patients, and the summary statistics for the VPIQL measurements are given in Table 7.40.

(a) Based on the information in Table 7.42, is it reasonable to assume that ???????? = ?????????

Why?

(b) Compute the appropriate value of ????????(????̄ − ????̄) and determine its degrees of freedom.

(c) Determine the rejection region for testing ????0 ∶ ???????? ≤ ???????? when ???? = 0.01.

(d) Compute the value of ????obs and its approximate ????-value.

(e) Is there sufficient statistical evidence to conclude ???????? > ????????? Why?

(f) Compute a 95% confidence interval for ???????? − ????????.