To enable alarm standards to be easily set up in Shewheart control chart.
A quality control method includes a step (S102) of calculating the mean value X and standard deviation σ of quality control data; a step (S106) of removing abnormal data out of a region of mean value×±4σ; a step (S108) of calculating the degree of estrangement between the calculated means value X, where the abnormal data have been removed and a usual target value by the use of the standard deviation σ; a step of calculating N so as to set the ratio of the number of data out of a region of a reference value±(2.5+0.1×N)σ to all the number of data at 0.015 or below:1, where the calculated mean value is made to serve as the reference value when the degree of estrangement is large, or a usual target value is made to serve as the reference value when the degree of estrangement is small; a step of setting up a reference value±(2.5+0.1×N)σ as alarm standards; and a step of forming quality alarm information when data out of the alarm standards appear.
Toshio Morita
Yoshihei Nakamura
Yutaka Horii
Hisato Noda
Masayuki Sakai
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