On Properties of Poisson Q Charts for Attributes

Article

Quesenberry, Charles P.   (1995, ASQC)   North Carolina State University, Raleigh, NC

Journal of Quality Technology    Vol. 27    No. 4
QICID: 11419    October 1995    pp. 293-303
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Article Abstract

The sensitivity of four tests on Shewhart Q charts and of specially designed EWMA and CUSUM Q charts to detect one-step permanent shifts of a Poisson parameter has been studied. The usual test that signals for one point beyond three standard deviations on a Shewhart chart is found to have poor sensitivity, generally. The test that signals when four out of five consecutive points are beyond one standard deviation in the same direction on a Shewhart Q chart is found to be a good omnibus test. The EWMA and CUSUM Q charts are most sensitive to detect this particular type of instability and are about comparable in overall performance.

Keywords

Attributes control charts,Cumulative sum control chart (CUSUM),Exponentially weighted moving average control charts (EWMA),Q chart (quality score),Shewhart control chart


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