The shape of the distribution of the time required to get an oil change at a
10-minute oil-change facility is unknown. However, records indicate that the mean time is 11.2 minutes, and the standard deviation is 4.6 minutes
Choose the required sample size below.
A. The sample size needs to be greater than 30.
B. The normal model cannot be used if the shape of the distribution is unknown.
C. The sample size needs to be less than 30.
D. Any sample size could be used.
What is the probability that a random sample of n equals = 35 oil changes results in a sample mean time less than 10 minutes?.
(Round to four decimal places as needed.)
(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, at what mean oil-change time would there be a 10% chance of being at or below? This will be the goal established by the manager. There would be a 10% chance of being at or below nothing minutes.