This paper proposes a distribution-free (or nonparametric) control scheme to monitor a process output that contains two special\r\ncauses of variation called ââ?¬Å?block or batchââ?¬Â effects and ââ?¬Å?treatment or positionââ?¬Â effects. The scheme properties (control limits, false\r\nalarmrate, and in-control average run length) stay the same under any assumed continuous probability distribution. Formoderate\r\nsample sizes, these properties can be computed exactly from available tables without the need to estimate the mean or variance of\r\nthe process. The proposed monitoring scheme requires ranking the observations within blocks and using the method of analysis\r\nof means by ranks. The paper includes an illustrative example concerning the grinding process of silicon wafers used in integrated\r\ncircuits production
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