Economic-statistical design of 2-of-2 and 2-of-3 runs rule scheme



In this paper, we investigate the economic-statistical design method for the 2-of-2 runs rule and the 2-of-3 runs rule. The Markov chain approach is used to obtain the average run length and the process cycle time. In addition, a simplified algorithm is presented to search the optimal setting of the design parameters. A numerical example and sensitivity analysis are also provided to compare the performances of the runs rules. The results show that the use of runs rule scheme can reduce operating cost comparing with the Shewhart control chart while maintaining a good statistical performance. Copyright © 2008 John Wiley & Sons, Ltd.