For Questions use the following narrative
Narrative: Exit poll
Suppose a recent election exit pollster reports that "Forty-eight percent of the voters polled said they voted for Candidate A.The margin of error for this survey is plus or minus 2.5 percentage points." Assume the exit poll was designed and conducted correctly.
-{Exit poll narrative} About how many people were sampled?
A)40
B)1,600
C)16,000
D)Not enough information to tell.

Question

Quizplus · Accepted Answer

In order to calculate the margin of error, we need to know the sample size, which is not directly stated in the narrative. However, we can use the formula for margin of error to solve for n (sample size):
margin of error = z*sqrt(p*q/n)
where z is the z-score corresponding to the desired level of confidence (let's assume a 95% confidence level, so z = 1.96), p is the proportion of voters who said they voted for Candidate A (0.48), q is the complement of p (0.52), and n is the sample size.
Plugging in the given margin of error (0.025), we get:
0.025 = 1.96*sqrt(0.48*0.52/n)
Solving for n, we get:
n = (1.96^2)*(0.48*0.52)/(0.025^2) = 1,568
So the closest answer choice is B, 1,600.

For Questions Use the Following Narrative