Calculated Decisions

摘要

Consider the following examples of key quality cnaracteristics for different products: 1. Trace contaminant concentration in a semiconductor raw material.rn2. Noise level from a portable generator.rn3. Concentricity of an engine drive shaft.rn4. Distance to target for several points of an airplane wing profile.rn5. Breaking strength of an LCD screen.rn6. Customers expect the suppliers of these products to provide proof of process control and process capability. When suppliers create control charts and run capability analyses, they assume their data follow a normal distribution. However, the natural distribution of these quality characteristics-and hundreds more like them-is not the normal distribution. Therefore, standard textbook calculations for process capability and control charts that assume normality can be incorrect.