In a drilling operation, four factors (A, B, C, and D), each at three levels, are thought to be of importance in influencing the volume of crude oil pumped. Using an L9 orthogonal array, the factors A, B, C, and D are assigned to columns 1, 2, 3, and 4, respectively. The response variable showing the number of barrels (in thousands) pumped per day for each of the nine experiments is as follows:

Show the experimental design and the response variable for the corresponding experiments. Determine the main effects. Plot the average response curves. What are the optimal settings of the design parameters?

Experiment 1 234 5 678 9 Barrels per Day (thousands) 6.8 15.8 10.5 5.2 17.1 3.4 5.9 122 8.5