Suppose you want a defect profile for factor X1, in the presence of random variation in X2 and X3. A series of n = N Runs simulation runs is done at each of k points in a grid of equally spaced values of X1. (By default, k is set at 17.) At each grid point, suppose that there are m defects due to the specification limits. At that grid point, the defect rate is m/n. These defect rates are connected and plotted as a continuous function of X1.