Suppose that an internal report submitted to the managers at a bank in Boston showed that with 95 percent confidence, the proportion of the bank's customers who also have accounts at one or more other banks is between .45 and .51. Given this information, what sample size was used to arrive at this estimate?
A) About 344
B) Approximately 1,066
C) Just under 700
D) Can't be determined without more information.

Question

Quizplus · Accepted Answer

The sample size can be estimated using the formula for the confidence interval of a proportion: n = (Z^2 * p * (1-p)) / E^2. Here, Z is the Z-score for 95% confidence (1.96), p is the midpoint of the interval (0.48), and E is the margin of error (0.03). Solving this gives approximately 1,066.

Suppose That an Internal Report Submitted to the Managers at a Bank