5. The marketing manager of National Hardware is making an economic feasibility study for constructing a new store in a rapidly expanding suburban neighborhood. A sample of 135 families was randomly selected from the area, which has a mean family income of $23, 480 with a standard deviation of $1575.

a. Construct a 90% confidence interval for estimating the average family income of all the family in the potential market area.

b. What does this mean?

6. A producer of steel cables wants to test if the steel cables it produces have a breaking strength of 5,000 lb. A breaking strength of less than 5,000 lb would not be adequate, and to produce steel cables with breaking strengths of more than 5,000 lb would unnecessarily increase production costs. The producer takes a random sample of 64 pieces and finds that the average breaking strength is 5,100 lb and the sample standard deviation is 480lb. Should the producer accept the hypothesis that its steel cable has a breaking strength of 5,000 lb at the 5% level of significance?