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 shown below.

Process A

Process B

Sample mean

2.03.0Standard

deviation1.00.5

Sample size 1214

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. If we test the null hypothesis at the 1% level of significance, which of the following is the correct decision?

Multiple Choice

• Fail to reject the null hypothesis.
• Fail to reject the null hypothesis and conclude the means are different.
• Reject the null hypothesis and conclude the means are the same.
• Reject the null hypothesis and conclude the means are different.