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One-tailed test of hypothesis

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1) An automobile assembly line operation has a scheduled mean completion time, mean, of 12.8 minutes. The standard deviation of completion times is 1.2 minutes. It is claimed that, under new management, the mean completion time has decreased. To test this claim, a random sample of 44 completion times under new management was taken. The sample had a mean of 12.3 minutes. Assume that the population is normally distributed. Can we support, at the 0.01 level of significance, the claim that the mean completion time has decreased under new management? Assume that the standard deviation of completion times has not changed.
Perform a one-tailed test.
H0 mean =12.8
H1 mean <12.8
This is a z test
The value of the test statistic is
The critical value at the 0.01 level of significance: (round to at least three decimal places)
Can we support the claim that the mean completion time has decreased under new management?

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An automobile assembly line operation has a scheduled mean completion time, mean, of 12.8 minutes. The standard deviation of completion times is 1.2 minutes. It is claimed that, under new management, the mean completion time has decreased. To test this claim, a random sample of 44 completion times under new management was taken. The sample had a mean of 12.3minutes. Assume that the population is normally distributed. Can we support, at the 0.01level of significance, the claim that the mean completion time has decreased under new management? Assume that the standard deviation of ...

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