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A hydraulic press is operating correctly when the standard deviation of the pressure is less than 120 pounds-per-square-inch (psi).Suppose you take a random sample of 15 measurements throughout the day of the psi and find the standard deviation to be 148.Suppose you want to test whether the press is operating correctly.
-A random sample of size 10 is selected from a normal population,where the population standard deviation is unknown.Assume that a two-tailed test at the 0.10 significance level is to be used.For what value of t will the null hypothesis not be rejected?
A)to the left of -1.812 or to the right of 1.812
B)to the left of -1.372 or to the right of 1.372
C)to the left of -1.833 or to the right of 1.833
D)to the left of -1.383 or to the right of 1.383

Question

Quizplus · Accepted Answer

Since the population standard deviation is unknown, we need to use the t-distribution. The critical value of t for a two-tailed test with 9 degrees of freedom and 0.10 level of significance is 1.833. If the calculated t-value falls within the range of -1.833 to 1.833, we fail to reject the null hypothesis.

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