In a survey of 485 potential jurors one study found that 345

In a survey of 485 potential jurors, one study found that 345 were regular watchers of at least one crime-scene forensics television series. (a) Assuming that it is reasonable to regard this sample of 485 potential jurors as representative of potential jurors in the United States, use the given information to construct a 95% confidence interval for the true proportion of potential jurors who regularly watch at least one crime-scene investigation series. (Use Table 3 in Appendix A. Give the answer to three decimal places.)
( , )

Solution

p=350/485=0.722

Given a=0.05, |Z(0.025)|=1.96 (check standard normal table)

So 95% CI is
p±Z*[p*(1-p)/n]

--> 0.722±1.96*sqrt(0.722*(1-0.722)/485)

--> ( 0.6821272, 0.7618728)