Acta Mathematicae Applicatae Sinica, English Series

, Volume 19, Issue 3, pp 397–404 | Cite as

Continuity Adjustment for Control Charts for Attributes

  • L. K. Chan
  • T. K. Mak
  • B. Tao
Original papers


A unified approach is proposed for making a continuity adjustment on some control charts for attributes, e.g., np-chart and c-chart, through adding a uniform (0, 1) random observation to the conventional sample statistic (e.g., \( n\hat{p}_{i} \) and c i ). The adjusted sample statistic then has a continuous distribution. Consequently, given any Type I risk α (the probability that the sample statistic is on or beyond the control limits), control charts achieving the exact value of α can be readily constructed. Guidelines are given for when to use the continuity adjustment control chart, the conventional Shewhart control chart (with ±3 standard deviations control limits), and the control chart based on the exact distribution of the sample statistic before adjustment.


Control charts for attributes continuity adjustments np, p, and c control charts statistical process control 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  1. 1.Department of Management SciencesCity University of Hong KongKowloonHong Kong
  2. 2.Department of Decision Sciences & M.I.S.Concordia UniversityMontrealCanada
  3. 3.Academy of Mathematics and System SciencesChinese Academy of SciencesBeijingChina

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