Answer:
A sample of 796 is needed.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of , and a confidence level of , we have the following confidence interval of proportions.
In which
z is the zscore that has a pvalue of .
The margin of error is:
In this question, we have that:
91% confidence level
So , z is the value of Z that has a pvalue of , so .
How large should a sample be if the margin of error is .03 for a 91% confidence interval
We need a sample of n, which is found when . So
Rounding up
A sample of 796 is needed.