Question

According to the Air Transport Association of America, the average operating cost of an MD-80 jet airliner is $2,087 per hour. Suppose the operating costs of an MD-80 jet airliner are normally distributed with a standard deviation of $166 per hour.

(Round the value of z to 2 decimal places. Round your answers to 2 decimal places.)

(a) At what operating cost would only 20% of the operating costs be less? $enter the dollar amount at which only 20% of the operating costs would be less (b) At what operating cost would 65% of the operating costs be more? $enter the dollar amount at which 65% of the operating costs would be more (c) What operating cost would be more than 85% of operating costs? $enter the dollar amount that would be more than 85% of operating costs

Answer 1

Given data are population mean = $2087 per hour

Population sd =$166 per hour

a) given = 20%

At = 0.20 in left tail from z table z = -0.84

Then operating cost

=2087 - 0.84 × 166

= 2087-139.44

=$ 1947.56 which only 20% of the operating cost would be less

b) given = 65%

Then at =35% in left tail from z table z= - 0.39

Then operating cost

= 2087- 0.39× 166

= 2087- 64.74

=$ 2022.26 which 65% of the operating cost would be more

c) given =85%

Then at =15% in right tail from z table z=1.04

the operating cost

= 2087+1.04×166

= 2087+ 172.64

=$2259.64 would be more than 85% of operating cost