Question

A time study of a factory worker has revealed an average observed time of 3.20 minutes, with a standard deviation of 1.28 minutes. These figures were based on a sample of 45 observations. Assume that the firm wants to be 90% confident that the standard time is within 5% of the true value. (Round all intermediate calculations to two decimal places before proceeding with further calculations.) | Based on the given information and the given confidence level and accuracy level, the number of observations that would be necessary for the time study = observations (round your response up to the next whole number). Enter your answer in the answer box and then click Check Answer. nart

Answer 1

FORMULA:
N = (((Z * SAMPLE STANDARD DEVIATION) / (DESIRED ACCURACY PERCENTAGE / 100) * SAMPLE MEAN))^2

OBSERVED MEAN TIME = 3.2
STDEV = 1.28
NUMBER OF SAMPLES = 45
CONFIDENCE INTERVAL 90, WHICH GIVES A Z VALUE OF 1.64
DESIRED ACCURACY PERCENTAGE = 5

N = ((1.64 * 1.28) / (5 / 100 * 3.2))^2 = 172.1344 OR 173