A manager who is conducting a time study now needs an accuracy of ±0.1 minutes, rather than ±0.2 minutes as in the past. Because of this change in accuracy, the adequate sample size becomes
A) one-fourth as large
B) one-half as large
C) twice as large
D) four times as large
E) none of the above

Question

Quizplus · Accepted Answer

The formula for calculating the sample size required for a time study is:
n = (zα/2 * σ / d)²
where n is the sample size, zα/2 is the z-value for a given level of confidence, σ is the standard deviation of the population, and d is the desired level of precision (d = ±0.1 minutes in this case).
Since the desired level of precision has decreased by half (from ±0.2 to ±0.1), the value of d in the formula will be halved. This means the sample size will need to be four times as large to maintain the same level of confidence. Therefore, the answer is D, four times as large.

A Manager Who Is Conducting a Time Study Now Needs