A manager who is conducting a time study now needs an accuracy of ±0.1 minutes, rather than ±0.05 minutes as in the past. Because of this change in accuracy, the new required sample size becomes:
A) one-fourth as large.
B) one-half as large.
C) twice as large.
D) four times as large.
E) one-tenth larger.

Question

Quizplus · Accepted Answer

The required sample size for a given level of accuracy is inversely proportional to the square of the desired margin of error. Therefore, if the margin of error changes from ±0.05 to ±0.1, the square of the ratio of the old margin to the new margin is (0.05/0.1)^2 = (1/2)^2 = 1/4. This means the new required sample size is one-fourth as large as before.

A Manager Who Is Conducting a Time Study Now Needs