品种退化: degeneration of seed strainsdegeneration of varietydegradation of breeddegradation of varietydeterioration of strainsdeterioration of varietystandard aberrationvariety degeneration
Traditional methods for measuring fraction of nonconformities become inapplicable for those high quality processes since any manufacturing sample of reasonable size likely contains no defective product items 然而，由于在这些高质量制程（不良品种通常用百万分之一?衡量单位）所取出适当大小的样本中几乎没有不良品，因此常规用来衡量这些低不良率制程的方法变得没有效率且不适用。
