According to internal testing done by the Get-A-Grip tire company, the mean lifetime of tires sold on new cars is 23,000 miles, with a standard deviation of 2,500 miles.
a) If the claim by Get-A-Grip is true, what is the mean of the sampling distribution of for samples of size n = 4?
b) If the claim by Get-A-Grip is true, what is the standard deviation of the sampling distribution of for samples of size n = 4?
c) If the distribution of tire life is approximately normal, what is the probability that the mean of a random sample of size n = 4 of tire lifetimes will be less than 20,000 miles?

Question

According to internal testing done by the Get-A-Grip tire company, the mean lifetime of tires sold on new cars is 23,000 miles, with a standard deviation of 2,500 miles. 
a) If the claim by Get-A-Grip is true, what is the mean of the sampling distribution of  for samples of size n = 4? 
b) If the claim by Get-A-Grip is true, what is the standard deviation of the sampling distribution of  for samples of size n = 4? 
c) If the distribution of tire life is approximately normal, what is the probability that the mean of a random sample of size n = 4 of tire lifetimes will be less than 20,000 miles?

Quizplus · Accepted Answer

The Answer is a) a) b) c)

b)

c)

According to Internal Testing Done by the Get-A-Grip Tire Company