the shape of the distribution of the time required to get an oilchange at a 20?-minute ?oil-change facility is unknown.? However,records indicate that the mean time is 21.2 minutes?, and thestandard deviation is 3.4 minutes.
Complete parts ?(a) through (c).
?(a) To compute probabilities regarding the sample mean usingthe normal? model, what size sample would be? required?
?(b) What is the probability that a random sample of n=45 oilchanges results in a sample mean time less than 20 ?minutes?
?(c) Suppose the manager agrees to pay each employee a? $50bonus if they meet a certain goal. On a typical? Saturday, the?oil-change facility will perform 45 oil changes between 10 A.M. and12 P.M. Treating this as a random? sample, there would be a? 10%chance of the mean? oil-change time being at or below what? value?This will be the goal established by the manager.
