Abstract
In many instances attributes data must be used to monitor a manufacturing (or other) process that, in normal conditions, should operate at very low count levels for defects. Lucas (1989) has directed attention to this problem, and has investigated a new control scheme for low count-level processes. An alternative scheme is proposed, based on a Cumulative Sum (CUSUM) of the number (termed Run-Length) of successive samples having zero count-levels between samples having at least one count. Using the criterion of Average Run Length (the average number of samples until a signal is generated) comparisons of the Lucas scheme and the Run-Length CUSUM scheme indicate that ARL values for the Run-Length CUSUM can be up to 50% lower.
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References
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Bourke, P.D. Performance of cumulative sum schemes for monitoring low count-level processes. Metrika 39, 365–384 (1992). https://doi.org/10.1007/BF02614020
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DOI: https://doi.org/10.1007/BF02614020