Suppose you wish to estimate a population mean correct to within .20 with probability equal to .90. You do not know σ2, but you know that the observations will range in value between 30 and 34.
a. Find the approximate sample size that will produce the desired accuracy of the estimate. You wish to be conservative to ensure that the sample size will be ample to achieve the desired accuracy of the estimate.
b. Calculate the approximate sample size, making the less conservative assumption that the range of the observations is equal to 6σ.