1.An airline records flight delays in and out of Chicago O'Hare airport for a year. The average delay for these flights is 9.05 minutes with a standard deviation of 4.04 minutes. For a sample of 61 flights, 23% of flights will have an average delay less than how many minutes?
a.There is not enough information
b. 12.03
c. 6.07
d.9.43
e.8.67
2.As a result of the subprime mortgage crisis of 2008, approximately 11.81% of new mortgage originations went into foreclosure by 2009. Suppose in the Kalamazoo area there were 2,587 homes in which the mortgage originated during this period. What is the probability that less than 12.37% of the homes would be foreclosed on?
a.0.1887
b.>0.999
c.0.8113
d. 42.5921
e.0.5000
Solution:
Question 1)
Given:
Mean =
Standard Deviation =
Sample size= n= 61
Find sample mean such that:
Thus find z value such that:
P( Z< z) =0.23
Look in z table for Area = 0.2300 or its closest area and find corresponding z value.
Area -0.2296 is closest to 0.2300 and it corresponds to -0.7 and 0.04
thus z = -0.74
Now use following formula to find value:
Question 2)
Given:
p = 0.1181
n = 2587
Find:
Find z score for 0.1237
Thus we get:
Look in z table for z =0.8 and 0.08 and find corresponding area.
P( Z < 0.88) = 0.8106
closest answer is: 0.8113 thus correct answer is: 0.8113
Excel command gives accurate answer:
=NORM.S.DIST( z ,cumulative)
=NORM.S.DIST(0.882575,TRUE)
=0.8113
1.An airline records flight delays in and out of Chicago O'Hare airport for a year. The...
An airline records flight delays in and out of Chicago O'Hare airport for a year. The average delay for these flights is 9.85 minutes with a standard deviation of 3.27 minutes. For a sample of 58 flights, 16% of flights will have an average delay greater than how many minutes? 1) 13.1 2) There is not enough information to determine this. 3) 9.42 4) 6.6 5) 10.28 Please try and answer using a graphing calculator
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