In: Statistics and Probability
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 |
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