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Statistical process control procedures for correlated observations
Author(s) -
Harris Thomas J.,
Ross William H.
Publication year - 1991
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450690106
Subject(s) - statistical process control , series (stratigraphy) , correlation , statistics , statistical analysis , process (computing) , computer science , mathematics , econometrics , geology , paleontology , geometry , operating system
Measurements from industrial processes are often serially correlated. The impact of this correlation on the performance of the cumulative sum and exponentially weighted moving average charting techniques is investigated in this paper. It is shown that serious errors concerning the “state of statistical process control” may result if the correlation structure of the observations is not taken into account. The use of time series methods for coping with serially correlated observations is outlined. Paper basis weight measurements are used to illustrate the time series methodology.