Société de Physique et d'Histoire Naturelle de Genève
[en] Hotelling’s T2 control chart ; Variable Ratio Sampling schemes ; Markov Chain, Genetic Algorithms (GA).
[en] The Hotelling’s T2 control chart with variable parameters (VP T2) has been shown to have improved performance in detecting small process shifts when compared to the original fixed parameter T2 control chart (FRS T2). Practically, though, there are some difficulties in implementation since one needs to use two different measuring scales with the VP T2 chart. In this paper, we propose an alternative sampling scheme to the VP T2 chart. Here we allow the sampling interval h, the sample size n and control limit k to vary between minimum and maximum values while keeping the warning line fixed over time. This proposed method uses only one measurement scale instead of two, greatly increasing its ease of use. Using a mathematical model, we show that this proposed method yields designs that have properties of rapid detection of small and moderate shifts in the process and, in addition, are easy to apply.