The length of time to complete a door assembly on a automobile factory assembly line is normally distributed with mean = 6.7 minutes and standard deviation = 2.2 minutes. For a door selected at random, what is the probability the assembly line will be

a) 5 minutes or less

b) 10 minutes or less

c) between 5 and 10 minutes

d) more then 10 minutes

Solution: (a) Letbe the random length of time to complete a door assembly. The probability we are looking for is

(b) We need to find

(c) Now we need to find

(d) Finally,