The principal at Riverside High School would like to estimate the mean length of time each day that it takes allthe buses to arrive and unload the students. How large a sample is needed if the principal would like to assertwith 90% confidence that the sample mean is off by, at most, 7 minutes. Assume that s = 14 minutes based onprevious studies.
A) 11
B) 10
C) 12
D) 13

Question

Quizplus · Accepted Answer

The sample size needed is given by the formula:n = (Z^2 * s^2) / E^2where:Z is the z-score for the desired confidence levels is the sample standard deviationE is the margin of errorPlugging in the given values, we get:n = (1.645^2 * 14^2) / 7^2n = 11.02Since we cannot have a fraction of a sample, we round up to the nearest whole number, which is 11. Therefore, the correct answer is A.

The Principal at Riverside High School Would Like to Estimate