Amax Industries operates two manufacturing facilities that specialize in doing custom manufacturing work for the semiconductor industry. The facility in Denton, Texas, is highly automated, whereas the facility in Lincoln, Nebraska, has more manual functions. For the past few months, both facilities have been working on a large order for a specialized product. The vice president of operations is interested in estimating the difference in mean time it takes to complete a part on the two lines. To do this, he has requested that a random sample of 15 parts at each facility be tracked from start to finish and the time required be recorded.

The following sample data were recorded:

Denton, Texas Lincoln, Nebraska –x 1  56.7 hours –x 2  70.4 hours s1  7.1 hours s1  8.3 hours Assuming that the populations are normally distributed with equal population variances, construct and interpret a 95% confidence interval estimate.