Answer:
And rounded up we have that n=421
Step-by-step explanation:
We know that the sample proportion have the following distribution:
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 90% of confidence, our significance level would be given by and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
We assume that a prior estimation for p would be since we don't have any other info provided. And replacing into equation (b) the values from part a we got:
And rounded up we have that n=421