A national manufacturer of ball bearings is experimenting with two different processes for producing precision ball bearings. It is important that the diameters be as close as possible to an industry standard. The output from each process is sampled and the average error from the industry standard is calculated. The results are presented below: The researcher is interested in determining whether there is evidence that the two processes yield different average errors.
What is the decision at the 1% level of significance?
A) Reject the null hypothesis and conclude the means are different.
B) Reject the null hypothesis and conclude the means are the same.
C) Fail to reject the null hypothesis and conclude the means are the same.
D) Fail to reject the null hypothesis and conclude the means are different.

Question

A national manufacturer of ball bearings is experimenting with two different processes for producing precision ball bearings. It is important that the diameters be as close as possible to an industry standard. The output from each process is sampled and the average error from the industry standard is calculated. The results are presented below:  The researcher is interested in determining whether there is evidence that the two processes yield different average errors.
What is the decision at the 1% level of significance?
A) Reject the null hypothesis and conclude the means are different. 
B) Reject the null hypothesis and conclude the means are the same. 
C) Fail to reject the null hypothesis and conclude the means are the same. 
D) Fail to reject the null hypothesis and conclude the means are different.

Quizplus · Accepted Answer

Based on the results of the t-test with a 1% level of significance, if the calculated p-value is less than 0.01, we reject the null hypothesis and conclude that the means are different. In this case, the calculated p-value is 0.001, which is less than 0.01, so we reject the null hypothesis. Therefore, the best choice is A, rejecting the null hypothesis and concluding the means are different.

A National Manufacturer of Ball Bearings Is Experimenting with Two