SOLUTION: In 2004, a small dealership leased 21 Chevy impalas on 2-year leases. When the cars were returned in 2006, the mileage was recorded and the 21 cars had an average of 33,950 miles a

Question 255912: In 2004, a small dealership leased 21 Chevy impalas on 2-year leases. When the cars were returned in 2006, the mileage was recorded and the 21 cars had an average of 33,950 miles and a standard deviation of 11,866.
A) What is the null and alternate hypotheses to determine if leases exceed the national average of 30,000 miles?
Ho: u = 30,000
H1: u > 30,000
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B) Using alpha .10, what is the critical value for the hypothesis test?
Right-tail test with alpha = 10%: t = invT(0.90,20) = 1.325
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C) What is the test statistic?
t(33,950) = ((33,950-30000)/[11866/sqrt(21)] = 1.5254...
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D) Make a conclusion for the hypothesis test.
Since the test statistic is to the right of the critical value reject Ho.
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Cheers,
Stan H.
I was trying to figure out how you got 1.325 in part B without a calculator. I have T critical values and normal distribution table in front of me. Thanks!

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
I used a calculator to get the 1.325.
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I just now checked a t-chart and found the same value
for df=20 and significance level = 0.10.
Cheers,
Stan H.
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