Suppose a researcher, interested in obtaining an estimate of the average level of some enzyme in a certain human population, takes a sample of 10 individuals, determines the level of the enzyme in each, and computes a sample mean = 22. Suppose further it is known that the variable of interest is approximately normally distributed with a variance of 45. (a) Calculate 90% confidence limits for the population mean. (b) If 1% of the means were low indicating an anomaly or an irregularity, below what average enzyme level would a physician be concerned? (c) Ninety percent of the average enzyme levels are within the normal range, between what to average enzyme levels would be considered the normal range?
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