A time-study analyst has found the select time for a work element to be 14.0 minutes,with a sample standard deviation of 3.2 minutes.What is the minimum sample size needed if the estimate is to be within 4 percent of the average 95 percent of the time?
A) Fewer than 100
B) Greater than or equal to 100 but fewer than 140
C) Greater than or equal to 140 but fewer than 180
D) Greater than or equal to 180

Question

Quizplus · Accepted Answer

The sample size needed is:n = (Z^2 * s^2) / (E^2 * x^2)where:Z = the z-score for the desired confidence level (95% = 1.96)s = the sample standard deviation (3.2 minutes)E = the desired error (4% of the average = 0.04 * 14.0 minutes = 0.56 minutes)x = the average select time (14.0 minutes)Plugging in the values, we get:n = (1.96^2 * 3.2^2) / (0.56^2 * 14.0^2) = 139.96Therefore, the minimum sample size needed is 140.

A Time-Study Analyst Has Found the Select Time for a Work