SOLUTION: A small dealership leased 21 Suburu Outbacks on 2-year leases. Two years later, when the cars were returned, the mileage was recorded (see below). Is the dealer’s mean significan

Question 1188604: A small dealership leased 21 Suburu Outbacks on 2-year leases. Two years later, when the cars were returned, the mileage was recorded (see below). Is the dealer’s mean significantly different from the national average of 30,000 miles for 2-year leased vehicles, using the 10 percent level of significance? (a) What is the appropriate testing method? Please write down each step of hypothesis testing for this case. (b) Please solve this problem and show the process and the output file. (20 points total)
40060, 24960, 14310, 17370, 44740, 44550, 20250,
33380, 24270, 41740, 58630, 35830, 25750, 28910,
25090, 43380, 23940, 43510, 53680, 31810, 36780

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
This is testing means of a variable (mileage) against a specific mean. The sd can be calculated and if assumed to be an unbiased estimator of the population's, than a 1-sample t-test would be appropriate.
Ho: mileage= 30000
Ha: mileage ne 30000
alpha; 0.10 p{reject Ho|ho true}=0.10
test is a t-test (0.90, df=20)
critical value |t|>1.725
calculation the mean is
33950
s=11866
the output on a calculator t=1.53 p-value =0.14
also
t=(33950-30000)/11866/sqrt(21)
=3950*sqrt(21)/11866
=1.53
fail to reject Ho, insufficient evidence to deny the claim.
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