3 . discussing application of entropy in multivariate control chart , firstly , testing whether the correlation structure has changed by means of the mutual information approach . secondly , using approximately approach to discuss two estimators of conditional entropy . finally , establishing corresponding entropy chart 討論了熵在多變量控制圖中的應用,首先利用相互信息量的方法檢測相關陣是否變化,然后利用近似的方法討論了兩種條件熵的估計量,建立了相應的熵圖。