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.
Ball Bearings
Hypothesis Test: Independent Groups (t-test, pooled variance)
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.
Ball Bearings
Hypothesis Test: Independent Groups (t-test, pooled variance)
 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 p-value of 0.001, which is less than 0.01 level of significance, we reject the null hypothesis and conclude that there is evidence that the two processes yield different average errors. Therefore, Choice A is the correct answer.

A National Manufacturer of Ball Bearings Is Experimenting with Two