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 less than 100 minutes for his or her tires to be installed?

Question

Quizplus · Accepted Answer

To find the probability of a customer waiting less than 100 minutes, we calculate the Z-score using the formula Z = (X - μ) / σ, where X is the value of interest (100 minutes), μ is the mean (106.3 minutes), and σ is the standard deviation (18.5 minutes). The Z-score is (100 - 106.3) / 18.5 = -0.3411. Looking up this Z-score in a standard normal distribution table or using a calculator gives a probability of approximately 0.3669.

Costco Installs Automobile Tires on a First-Come First-Serve Basis