Question

The ages of commercial aircraft are normally distributed with a mean of 13.5 years and a standard deviation of 7.3 years. what percentage of individual aircraft have ages greater than 15 ​years? assume that a random sample of 49 aircraft is selected and the mean age of the sample is computed. what percentage of sample means have ages greater than 15 ​years?

Answer 1

Answer: The percent higher is 41.68%. If 49 planes were selected, 20 of them should be above 15 years.

To find the percent, we first need the z-score.

(15 - 13.5) / 7.3 = 0.21

Now, use a normal distribution table to find the percent above a score of 0.21. It will be 41.68%.

To find the number of 49 planes above this value, multiply 49 by 0.4168. You will have about 20.4 planes.