Chapter 2
Methods for Evaluating Quality


The front page of the Ashi News on April 17, 1979 compared the quality levels of Sony color TV sets made in Japanese plants and those made in the San Diego, California, plant. The quality characteristic used to compare these sets was the color density distribution, which affects color balance. Although all the color TV sets had the same design, most American customers thought that the color TV sets made in the San Diego plant were of lower quality than those made in Japan.

The distribution of the quality characteristic of these color TV sets was given in the Ashi News and is shown in Figure 2.1. As shown in Figure 2.1, the quality characteristics of the TV sets from Japanese Sony plants are normally distributed around the target value m. If a value of 10 is assigned to the range of the tolerance specifications for this objective characteristic, then the standard deviation of this normally distributed curve can be calculated and is about 10/6.

  • 2.1 Comparing the Quality Levels of Sony TV Sets Made in Japan and in San Diego
  • 2.2 Loss Function
  • Discussion: About Quality Loss Function
  • Exercise

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