Economic design of moving average control chart for non-normal data using variable sampling intervals

Abstract

In this article, we propose an economic design of moving average X control chart for non-normal quality characteristics using variable sampling intervals (VSI) policy. An expression for expected loss cost function is derived for continued and ceased process designs. The performance of two operational modes is compared numerically and the comparison between fixed sampling interval (FSI) and VSI control schemes is carried out. The VSI scheme is found to be superior to FSI scheme. As the number of sampling intervals increases, percentage saving in cost with respect to FSI design increases. The ceased VSI production process shows more saving with respect to continuous VSI production process. Percentage saving due to ceasing increases with increasing shift in the process. Also, the sample size increases with the decreasing values of shift. Overall, the ceased VSI moving average process design seems to be economically superior to other process designs.

The variable sampling interval run sumX‾control chart

“…Liu, Chen, Zhang, and Zi (2015) proposed adaptive phase II nonparametric EWMA chart with the VSI feature. In addition, Patil and Shirke (2015), Peng, Xu, and Reynolds (2015) and Seif, Faraz, and Sadeghifar (2015) applied VSI schemes on the moving average, generalized likelihood ratio and multivariate v 2 control charts, respectively.…”

Economic design of a nonparametric EWMA control chart for location

“…Saniga (1989) has obtained economic-statistical design of X and R chart, which gives economic design with improved statistical properties at slight increase in loss cost. The considerable work on economic design of control charts is also carried out by Banerjee & Rahim (1987), Reynolds Junior et al (1988), McWillims (1989, Koo & Case (1990), Bai & Lee (1998), Chou et al (2001), Chen (2004), Chen & Yeh (2006), Mahadik & Shirke (2007), Patil & Rattihalli (2009), Yeh & Chen (2010), Patil & Shirke (2015) and many others. The work by these researchers has made consistent improvement in the economic design of different types of control chart.…”