A leasing firm claims that the mean number of miles driven annually,
μ
, in its leased cars is less than
12620
miles. A random sample of
30
cars leased from this firm had a mean of
11399
annual miles driven. It is known that the population standard deviation of the number of miles driven in cars from this firm is
2660
miles. Assume that the population is normally distributed. Is there support for the firm's claim at the
0.05
level of significance?
Perform a onetailed test. Then fill in the table below.
Carry your intermediate computations to at least three decimal places, and round your responses as specified in the table. (If necessary, consult a list of formulas.)

H0: 12620
Ha: < 12620
Test Statistic :
Z = ( X  µ ) / ( σ / √(n))
Z = ( 11399  12620 ) / ( 2660 / √( 30 ))
Z = 2.514
Test Criteria :
Reject null hypothesis if Z < Z(α)
Critical value Z(α) = Z(0.05) = 1.645
Z < Z(α) = 2.514 < 1.645
Result : Reject null hypothesis
Conclusion 
We have sufficient evidence to support the claim that the mean number of miles driven
annually is less than 12620 miles
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