Question

# According to the Air Transport Association of America, the average operating cost of an MD-80 jet...

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 \$177 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 23% of the operating costs be less? \$ (b) At what operating cost would 65% of the operating costs be more? \$ (c) What operating cost would be more than 85% of operating costs? \$

 for normal distribution z score =(X-μ)/σx here mean=       μ= 2087 std deviation   =σ= 177.000

a)

To see the probability 0.23 in the standard normal table the cumulative z value is -0.74

 for 20th percentile critical value of z= -0.74 therefore corresponding value=mean+z*std deviation= 1956.02

b)

for top 65% values are at 35 percentile.

To see the probability 0.35 in the standard normal table the cumulative z value is -0.39.

 for 35th percentile critical value of z= -0.39 therefore corresponding value=mean+z*std deviation= 2017.97

c)

 for 85th percentile critical value of z= 1.04 therefore corresponding value=mean+z*std deviation= 2271.08