A Graphical Method to Control Process Capability

摘要: We suggest that one should focus on the process parameters (y, a) instead of capability index alone by using plots, both when defining what is meant a capable and deciding whether can be considered or not. First we introduce so called (S, y)-plot, to define region. The y)-plot based but focuses (µ, a). have earlier defined class indices, containing indices C 13 , pk pm k. By varying various as well regions with different properties are obtained.Under assumption normality two plots used interpreting results estimated in above mentioned for One these (b“, which generalization y)-plot. other confidence rectangle plot. This plot region y), plotted (S,y)-plot. These compared discussed from aspects. An advantage plot, alone, will instantly get visual information, simultaneously about location spread studied characteristics, information process. When non-capable, helpful trying understand if it variability, deviation target, need reduced improve capability. In this way proposed graphical methods give clear direction quality improvement.