The shape of the distribution of the time required to get an oil change at a 202
ID: 2947158 • Letter: T
Question
The shape of the distribution of the time required to get an oil change at a
2020?-minute
?oil-change facility is unknown.? However, records indicate that the mean time is
21.3 minutes21.3 minutes?,
and the standard deviation is
4.6 minutes4.6 minutes.
?(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
nequals=4040
oil changes results in a sample mean time less than
2020
?minutes?
Explanation / Answer
a) We require at least sample size of 30
b) P(z<(20-21.3)/4.6)*SQRT(40)
= p(Z<-1.51)
= 0.0652