A Tim Horton’s has recently opened up in Edmonton. Mean=6 mins, Standard deviation=2.6 mins

Question

a)What is the best probability that it takes less than 5.6 mins for a randomly selected car to be served after ordering? (Round to 4 decimal places)

b)What is the probability that it takes more than 6.9 mins for a randomly selected car to be served after ordering? (Round to 4 decimal places)

Answer 1

x = time to serve

x is N(6,2.6)

transform inequality to standard normal z = (x - mean)/SD

a) P(x < 5.6) = P(z < (5.6-6)/2.6) = P(z < -.15) = 0.4404

b) P(x > 6.9) = P(z > (6.9 - 6)/2.6) = P(z > 0.35) = P(z < -0.35) = 0.3632