Chapter 7.2, Problem 7E

An automotive supplier is considering changing its electrical wire harness to save money. The idea is to replace a current 20-gauge wire with a 22-gauge wire. Because not all wires in the harness can be changed the new wire must work with the current wire splice process .To determine whether the new wire is compatible, random samples were selected and measured with a pull lest A pull test measures the force required to pull the spliced wires apart. The minimum pull force required by the customer is 20 pounds. Twenty observations of the forces needed for the current wire are

28.8 24.4 30.1 25.6 26.4 23.9 22.1 22.5 27.6 28.1

20.8 27.7 24.4 25.1 24.6 26.3 28.2 22.2 26.3 24.4

Twenty observations of the forces needed for the new wire

14.1 12.2 14.0 14.6 8.5 12.6 13.7 14.8 14.1 13.2

12.1 11.4 10.1 14.2 13.6 13.1 11.9 14.8 11.1 13.5

(a) Does the current wire meet the customer’s specifications?

(b) Find an approximate 90% confidence interval for the difference of the means for these two sets of wire.

(c) Construct box-and-whisker diagrams of the two sets of data on the same figure.

(d) What is your recommendation for this company?