Modeling and Multivariate Methods - SAS

604 Visualizing, Optimizing, and Simulating Response Surfaces Chapter 24
The Simulator
Figure 24.54 Defect Parametric Profile
Let’s look closely at the SULFUR situation. You may need to enlarge the graph to see more detail.
First, note that the current defect rate (0.03) is represented in four ways corresponding to each of the four
curves.
For the red curve, Mean Shift, the current rate is where the red solid line intersects the vertical red dotted
line. The Mean Shift curve represents the change in overall defect rate by changing the mean of SULFUR.
One opportunity to reduce the defect rate is to shift the mean slightly to the left. If you use the crosshair
tool on this plot, you see that a mean shift reduces the defect rate to about 0.02.
For the blue curve, Std Narrow, the current rate represents where the solid blue line intersects the two
dotted blue lines. The Std Narrow curves represent the change in defect rate by changing the standard
deviation of the factor. The dotted blue lines represent one standard deviation below and above the current
mean. The solid blue lines are drawn symmetrically around the center. At the center, the blue line typically
reaches a minimum, representing the defect rate for a standard deviation of zero. That is, if we totally
eliminate variation in SULFUR, the defect rate is still around 0.003. This is much better than 0.03. If you
look at the other Defect parametric profile curves, you can see that this is better than reducing variation in
the other factors, something we suspected by the SD value for SULFUR.
For the green curve, LSL Chop, there are no interesting opportunities in this example, because the green
curve is above current defect rates for the whole curve. This means that reducing the variation by rejecting
parts with too-small values for SULFUR will not help.