Answer : 0.0129
Step-by-step explanation:
Given : Based on FAA estimates the average age of the fleets of the 10 largest U.S. commercial passenger carriers is years and standard deviation is
years.
Sample size :
Let X be the random variable that represents the age of fleets.
We assume that the ages of the fleets of the 10 largest U.S. commercial passenger carriers are normally distributed.
For z-score,
For x=14
By using the standard normal distribution table , the probability that the average age of these 40 airplanes is at least 14 years old will be :-
Hence, the required probability = 0.0129