1. A study was conducted to see if two groups of subjects

were equally likely to have a particular disease. For 99

subjects in group A, 23 had the disease, and for 105 sub-

jects in group B, 44 had the disease. You may assume a

random sample was taken from each group, and that the

groups are independent.

(a) Find the lower bound of the 95% confidence interval

for the difference in proportions of subjects with the

disease for group A vs. B.

(b) Find the upper bound of the 95% confidence interval

for the difference in proportions of subjects with the

disease for group A vs. B.

(c) Interpret your interval from (a/b) in terms of the

problem

(d) Does your interval suggest that group

A

is more likely

to have the disease?

(e) What is the largest significant difference in probabil-

ity of having the disease you expect these two groups

to have based on your confidence interval?

(f) If we increased our confidence interval to 99%, would

our interval widen or narrow?