A methods and measurement analyst wants to develop a time standard for a certain task. In a preliminary study, he observed one worker perform the task six times with an average observed time of 20 seconds and a standard deviation of 2 seconds.
How many observations should be made if he wants to be 95.44 percent confident that the maximum error in the observed time is 1 second?
A)3
B)4
C)13.3
D)16
E)25

Question

Quizplus · Accepted Answer

To achieve a 95.44% confidence level with a maximum error (E) of 1 second and a standard deviation (σ) of 2 seconds, the formula for the sample size (n) is n = (Zσ/E)^2. For a 95.44% confidence level, Z is approximately 2 (from the Z-table for a normal distribution, corresponding to the closest to 95.44% confidence level). Plugging the values into the formula gives n = (2*2/1)^2 = 16.

A Methods and Measurement Analyst Wants to Develop a Time