Question

Costco installs automobile tires on a first-come first-serve basis. the total time a customer needs to wait for the installation to be completed follows the normal distribution with a mean time of 106.3 minutes and a standard deviation of 18.5 minutes. what is the probability that a randomly selected customer will wait between 80 and 95 minutes for his or her tires to be installed?

Answer 1

Given:
μ=106.3 minutes
σ=18.5 minutes
Need to find
P(80<x<95)=>
P(x)=Z((95-&mu;)/&sigma;)-Z((80-&mu;)/&sigma;)
=Z(-0.61081)-Z(-1.42162)
=0.27066-0.077568
=0.1931
Therefore probability of customers waiting between 80 and 95 minutes is 0.1931