Question

The time it takes to train a newly hired telephone sales representative is normally distributed with a mean of 136 hours and a standard deviation of 8.9 hours. what is the probability that training for a given individual will last between 130 and 140 hours?

Answer 1

Using z-scores for 130 and 140 hours, and a standard normal distribution table, the cumulative probabilities for 130 and 140 hours are 0.254 and 0.673 respectively.
The required probability is 0.673 - 0.254 = 0.42 to 2 d.p.