Question

The shape of the distribution of the time required to get an oil change at a 20​-minute ​oil-change facility is unknown.​ However, records indicate that the mean time is 21.4 minutes​, and the standard deviation is 3.7 minutes. Complete parts ​(a) through ​(c). ​(a) To compute probabilities regarding the sample mean using the normal​ model, what size sample would be​ required? ​(b) What is the probability that a random sample of nequals35 oil changes results in a sample mean time less than 20 ​minutes? ​(c) Suppose the manager agrees to pay each employee a​ $50 bonus if they meet a certain goal. On a typical​ Saturday, the​ oil-change facility will perform 35 oil changes between 10 A.M. and 12 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?

Answer 1