Figure 4.

Influences of QC rule determinants on each other. Red plain single arrow: increases; red plain double arrow: vary in similar sense; black dotted single arrow: decreases; black dotted double arrow: vary in opposite sense, which means that when QC rules increase (from 12S to 12.5S to 13S), Ped decreases (not desirable) and Pfr decreases (desirable). EZ Rules 3 QC design software; Ped = probability of error detection; Pfr = probability of false rejection; QC = quality control; σ = sigma metric; TEa = total allowable error; TEo = observed total error.