均值向量与协差阵联合控制的处理方法

On the Treatment of Joint Control for Mean Vector and Covariance Matrix

经典的多元质量控制一直沿袭一元质量控制的思路，分别对均值向量和协差阵进行控制，这种处理方法给现场使用带来很多不便。作者开发的ζ─η图实现了在一个图上对均值向量和协差阵进行联合控制，不仅简化了作图方法，而且有利于揭示工序异常变化的原因。

Classical Multivariate Quality Control has adopted the approach to univariate case by controlling mean vector and covariance matrix separately,which is not convenient to on-site application. In order to overcome the disadvantages inherent in the classical situation, the authors develope a method named ζ-η chart to control mean vector and covariance matrix simultaneously,not onty simplifying the charting process, but also being easy to expose the cause of assignable process.