# Question

An efficiency expert wants to determine the aver-age amount of time it takes a pit crew to change a set of four tires on a race car. Use the formula for n in Exercise 11.6 to determine the sample size that is needed so that the efficiency expert can assert with probability 0.95 that the sample mean will differ from µ, the quantity to be estimated, by less than 2.5 seconds. It is known from previous studies that σ = 12.2 seconds.

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