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.
Process A Process B
Mean 0.002mm 0.0026mm
Standard Dev 0.0001mm 0.00012mm
Sample Size 12 14
assume that the population standard deviation are equal test the hypothesis that the two population means are equal using the 0.05 level