Assignment:
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. Is this sample adequate in size for the firm to be 99% confident that the standard time is within {5% of the true value? If not, what should be the proper number of observations?
Provide complete and step by step solution for the question and show calculations and use formulas.