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. Assume that the population standard deviations are equal. This example is what type of test?
A) One sample test of means.
B) Two sample test of means.
C) Paired t-test.
D) 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 calculated. The results are presented below.  The researcher is interested in determining whether there is evidence that the two processes yield different average errors. Assume that the population standard deviations are equal. This example is what type of test?
A) One sample test of means. 
B) Two sample test of means. 
C) Paired t-test. 
D) Test of proportions.

Quizplus · Accepted Answer

The experiment involves comparing two different processes, hence a two-sample test of means is appropriate. The researcher wants to determine whether the average errors from the two processes are different, assuming equal population standard deviations. Therefore, a two-sample t-test with equal variances can be used.

A National Manufacturer of Ball Bearings Is Experimenting with Two