Question

An airline records flight delays in and out of Chicago O'Hare airport for a year. The average delay for these flights is 12.66 minutes with a standard deviation of 4.17 minutes. For a sample of 77 flights, 91% of flights will have an average delay less than how many minutes?

Question 3 options:

	1) 13.3
	2) 18.25
	3) 7.07
	4) 12.02
	5) There is not enough information to determine this.

Answer 1

Solution,

Given that,

mean = = 12.66

standard deviation = = 4.17

n = 77

= = 12.66

= / n = 4.17/ 77 = 0.48

Using standard normal table,

P(Z < z) = 91%

= P(Z < z) = 0.91  

= P(Z < 1.34) = 0.91

z = 1.34

Using z-score formula  

= z * +

= 1.34 *0.48 + 12.66

= 13.3

correct option is = 1)