The yield of a chemical process is being studied. The two most important variables are thought to be the pressure and the temperature. Three levels of each factor are selected, and a factorial experiment with two replicates is performed. The yield data follow: Temperature Pressure
200 215 230
150 90.1 90.5 89.9
90.3 90.6 90.1
160 90.5 90.8 90.4
90.7 90.9 90.1
170 90.4 90.7 90.2
90.2 90.6 90.4

(a) Analyze the data and draw conclusions. Show your ANOVA table. Use α = 0.05.
(b) Prepare and show appropriate residual plots and comment on the model’s adequacy.
(c) Under what conditions would you operate this process?

An external consultant recommends that a plant installs a bank of capacitors for power factor correction. this will reduce the peak electrical demand charges by an average of 93 kw every month. the plant current pays $13 per kw in peak demand charges. the capacitor bank will include 223 kw of fixed capacitors, and 183 of variable capacitors. the fixed capacitors cost $59 per kw, and the variable capacitors will cost $65 per kw. the consultant charges 21% of the equipment costs to install the capacitors. because this project will reduce the demand for the electric utility, they are prepared to provide a one-time rebate of $42 per kw of reduced demand. what is the simple payback period for this project (in years)?