Question

8. Assume that the length of time needed to change the oil in a car at Fiona's Service Station is normally distributed with mean u = 15 minutes, and a standard deviation o = 5 minutes. If Fiona decides to offer a discount to those customers whose cars take the longest 20% of servicing time, what is the cutoff for the time required to receive the discount? EXCEL COMMAND

Answer 1

P=20%=0.2

$\mu$=15

$\sigma$=5

Using excel,

=NORM.INV(0.2,15,5)

=10.792

Therefore, answer is 10.792