Managers at an automobile manufacturing plant would like to examine the mean completion time, u, of an assembly line operation.

Question

Managers at an automobile manufacturing plant would like to examine the mean completion time, u, of an assembly line operation. The past data indicate that the mean completion time is 41 minutes, but the managers have good reason to believe that this value has decreased. The managers plan to perform a
statistical test.
After choosing a random sample of assembly line completion times, the managers compute the sample mean completion time to be 39 minutes. The standard deviation of the population of completion times can be assumed not to have changed from the previously reported value of 3 minutes.
Based on this information, complete the parts below.
(a) What are the null hypothesis Ho and the alternative hypothesis H₁ that should be used for the test?
H:0
H₁ :0
(b) Suppose that the managers decide not to reject the null hypothesis. What sort of error might they be making?
Suppose the true mean completion time for the assembly line operation is 37 minutes. Fill in the blanks to describe a
Type II error.
the hypothesis that u is
A Type II error would be

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