## (Solution Document) Consider a cystic fibrosis trial in which 351 people participated. 77% of the patients did better on the drug than on the placebo.

3. Consider a cystic fibrosis trial in which 351 people participated. 77% of the patients did better on the drug than on the placebo. Answer the following questions by hand and using the tables in the back of the book.

a) Among the 351 patients who were in the trial, how many of them did better on the drug than on the placebo?

b) Verify that both np >? 5 and nq >? 5.

c) Construct a 95% confidence interval estimate of the proportion of all people with cystic fibrosis who will do better on the drug than on the placebo.

d) Construct a 90% confidence interval estimate of the proportion of all people with cystic fibrosis who will do better on the drug than on the placebo.

e) As the level of confidence decreases, and all other values remain unchanged, what happens to the width of the confidence interval?

f) If the level of confidence stays constant and the sample size increases, and all other values remain unchanged, what happens to the width of the confidence interval?

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