Question

Trucks in a delivery fleet travel a mean of 120 miles per day with a standard deviation of 19 miles per day. The mileage per day is distributed normally. Find the probability that a truck drives between 91 and 133miles in a day. Round your answer to four decimal places.

Answer 1

Solution :

Given that ,

mean = = 120

standard deviation = = 19

P( 91 < x < 133) = P[(91 - 120)/ 19 ) < (x - ) /  < (133 - 120) / 19 ) ]

= P(-1.53 < z < 0.68)

= P(z < 0.68) - P(z < -1.53)

Using z table,

= 0.7517 - 0.0630

= 0.6887