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Continuous Process Improvement with Observational Studies

Summary: The essential feature of an observational study performed on a process is that data are collected without deliberately changing the process. Control charts, a type of observational study, have traditionally been used to establish and maintain process stability. Once stability is achieved, charting controls the process variability but does not reduce it further. This paper proposes the use of charting techniques in conjunction with observational studies for continuous variation reduction, that is, continuous improvement. The basic strategy is to devise a sampling design that identifies the largest sources of variation. Then as improvements are made, the sampling designs and corresponding analysis methods are updated. Consequently, most of the charting effort becomes an off-line activity. The necessity of up-front planning is also discussed.

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  • Topics: Sampling
  • Keywords: Variation,Sampling plans
  • Author: Hamada, M.; Mackay, R.J.; Whitney, J.B.
  • Journal: Journal of Quality Technology