Question

In a survey of 3107 adults aged 57 through 85​ years, it was found that 83.9% of them used at least one prescription medication.

Construct a​ 90% confidence interval estimate of the percentage of adults aged 57 through 85 years who use at least one prescription medication.

Answer 1

sample size          n=	3107
sample proportion p̂ =x/n=	0.8390
std error se= √(p*(1-p)/n) =	0.0066
for 90 % CI value of z=	1.645
margin of error E=z*std error   =	0.0108
lower bound=p̂ -E                       =	0.8282
Upper bound=p̂ +E                     =	0.8498
from above 90% confidence interval for population proportion =(0.8282 , 0.8498)