conclusion

The purpose of this paper is to investigate the ANF, ANS, ANI, and AATS statistical measures by applying variable sampling schemes in the U control chart. The U control chart is the statistical process control tools and used to count the number of defects in samples of a product. In designing variable sampling schemes, the range of sample size and/or sampling interval is unpredictable. Variation in sampling may be unpleasant from an operational viewpoint, but as shown, significant statistical improvement has been generated in the process. In this paper, the design of the sampling schemes and evaluation of statistical measures was done based on the Markov chain approach and transition probability of different process states. Also, by comparing the numerical results, the VSSI sampling scheme, which uses two sample sizes and two sampling intervals, compared with other schemes, has led to more reduction in the statistical measures and increase efficiency in the U control chart. Therefore, the significant advantage of the VSSI sampling scheme with other schemes, especially the FSSI, recommend in practical applications for more accuracy and better results.