Assume we 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. (k is generally 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. With normal weighted, these are done in a weighted fashion. These defect rates are connected and plotted as a continuous function of X1.