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 measured in millimeters. The results are presented next. The researcher is interested in determining whether there is evidence that the two processes yield different average errors. The population standard deviations are unknown but are assumed equal. This example is what type of test?
A)A one-sample test of means
B)A two-sample test of means
C)A paired t-test
D)A test of proportions

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 measured in millimeters. The results are presented next.  The researcher is interested in determining whether there is evidence that the two processes yield different average errors. The population standard deviations are unknown but are assumed equal. This example is what type of test?
A)A one-sample test of means 
B)A two-sample test of means 
C)A paired t-test 
D)A test of proportions

Quizplus · Accepted Answer

The experiment involves comparing two different processes for producing ball bearings, and the researcher is interested in determining whether there is evidence that the two processes yield different average errors. Therefore, the appropriate test to use is a two-sample test of means. The fact that the population standard deviations are assumed to be equal suggests that a pooled t-test should be used.

A National Manufacturer of Ball Bearings Is Experimenting with Two