Applying SVSSI sampling scheme to np-chart to decrease the time of detecting shifts using Markov chain approach and Monte Carlo simulation

One of the main criteria for judging the power of control charts is their ability to perform fast detection of deviations and shifts in the process. Average Time to Signal (ATS) and Adjusted Average Time to Signal (AATS) are among such criteria calculated under a certain state and assumption. Several studies have shown that based on the idea of variable design for control charts and by demarcating the limits between safe and unsafe regions, quick discovery of shifts is facilitated and sensitivity to small changes increases. In this paper, a new variable sampling scheme with three sample sizes and two di erent sampling intervals, called SVSSI, is developed to increase the efficiency of the control chart np. Through various numerical examples, the performance of this scheme is evaluated by calculating ATS and AATS values through the application of Markov chain method. Monte Carlo simulation method is used to validate the results of Markov chain method of SVSSI sampling scheme. In comparison with other schemes, SVSSI exhibits better performance in all conditions. © 2022 Sharif University of Technology. All rights reserved.