The double sampling S² chart with estimated process variance

ABSTRACT

This paper proposes useful exact bounds for the parameters of the double sampling S² chart with known process variance and it also investigates the properties of the double sampling S² chart with estimated process variance, in terms of the average run length, the standard deviation of the run length and the average sample size, providing a numerical comparison with the known process variance case. It also provides guidelines to systematically design the double sampling S² chart both with known and estimated process variance and proposes two optimal design procedures with estimated process variance, for (a) minimizing the out-of-control average run length and (b) minimizing the out-of-control average sample size.

KEYWORDS:

• Average sample size
• control chart
• estimated parameter
• run length

Acknowledgments

The authors thank the anonymous referees and the editor for their valuable suggestions which helped to improve the quality of the final manuscript.