Question

Question 24 A safety engineer at Abu Dhabi international airport wishes to find the 98.26% confidence interval for the average flight hours before major maintenance is required for her feet of aircrafts. The population standard deviation of the flight hours until major maintenance is 35 hours. Assuming that a sample was selected from a normally distributed population. How many aircrafts should be included in her sample to obtain a population average accurate within 18 hours? [3 Marks

Answer 1

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24.

Margin of error , E <= Z*Stdev/sqrt(n)

Z for 98.26% is 2.3781. We looked up the Z for a cumulative prob of .5+.9826/2 = .9913

SO, E = 18 hours <= 2.3781*35/sqrt(n)

sqrt(n) >= 2.3781*35/18 = 4.62408

Squaring both sides, n >= 21.38 or n = 22 ( see the inequality sign- we need to round off to next higher integer)

Answer: a. 22

25.

P(Candy|Coffee)
= total number of candy and coffee baskets/ total coffee baskets
= 12/(10+8+12)
= 2/5

Answer: 4) 2/5