1) A manager evaluates effectiveness of a major hardware upgrade by running a certain process 40 times before the upgrade and 40 times after it. Based on these data, the average running time is 8.6 minutes before the upgrade, 7.3 minutes after it. Historically, the standard deviation has been 1.8 minutes, and presumably it has not changed. Construct a 90% confidence interval showing how much the mean running time reduced due to the hardware upgrade.

2) The article "Wear in Boundary Lubrication" (S. Hsu, R.Munro, and M. Shen, Journal of Engineering Tribology, 2002: 427-441) discuses several experiments involving various lubricants. In one experiment, 45 steel balls lubricated with purified paraffin were subjected to a 40 kg load at 600 rpm for 60 minutes. The average wear, measured by the reduction in diameter, was 673.2 m, and the standard deviation was 14.9 m. Assume that the specification for a lubricant is that the mean wear be less than 675 m. Find the P- value for testingH₀ : 675 versus H₁ :<675. What can we conclude based on the P- value?