Question

The MAX light rail in Portland, OR has a waiting time that is normally distributed with a mean waiting time of 4.22 minutes with a standard deviation of 1.7 minutes. A random sample of 35 wait times was selected, what is the probability the sample mean wait time is under 3.74 minutes? Round answer to 4 decimal places

Answer 1

Solution :

Given that ,

mean = = 4.22

standard deviation = = 1.7

= / n = 1.7 / 35 = 0.2874

P( < 3.74) = P(( - ) / < (3.74 - 4.22) / 0.2874)

= P(z < -1.6701)

= 0.0474

Probability = 0.0474