Answer
($67.5,72.5$)
Work Step by Step
The standard deviation is not given in this problem, so we must use a
confidence interval program that does not involve standard deviation.
Hence first we must find the number of people who answered yes:
$0.7\cdot1501=1051$
Plugging in this together with the population size of $241$ million Americans, into a confidence interval calculator, we can find that the lower limit is $70−2.5=67.5$ and that the upper limit is $70+2.5=72.5$.
This is our $95$ percent confidence interval.
