construct a 90​% confidence interval estimate of the percentage of cell phone users

Question

A study of

420 comma 003420,003

cell phone users found that

131131

of them developed cancer of the brain or nervous system. Prior to this study of cell phone​ use, the rate of such cancer was found to be

0.04480.0448​%

for those not using cell phones. Complete parts​ (a) and​ (b).

a. Use the sample data to construct a

9090​%

confidence interval estimate of the percentage of cell phone users who develop cancer of the brain or nervous system.

 

nothin​(Round to three decimal places as​ needed.)