Traditionally, alert levels and action limits are established, using a mean of 2 or 3 standard devia-tions (SDs) to render certain degrees of assurance that the classified environments are in control. This method hinges on the assumption that the data or data after a transformation such as logarithmic are normally distributed.
[size=14.6667px]传统上,警报级别和行动限制是建立的,使用2或3个标准差(SDs)的平均值来在一定程度上确保分类环境得到控制。这种方法依赖于假设数据或转换后的数据,如对数,是正态分布的。