Authors: R Noorossana Ali Deheshvar Maryam Shekary A
Publish Date: 2015/09/15
Volume: 84, Issue: 5-8, Pages: 1303-1312
Abstract
In this article a modified version of variable sample size and sampling interval chart using three sampling intervals and two sample sizes called the VSSIt control chart is proposed to overcome the weakness of the standard Shewhart SS control chart in detecting small and moderate shifts In order to evaluate the performance of the proposed scheme average time to signal ATS average number of observations to signal ANOS and average number of samples to signal ANSS are used Using this control chart can reduce the ATS value around 68 27 7 and 183 time unit sampling interval of the SS chart in detecting shift of size 025 05 075 and 1 standard deviation respectively The performance of the constructed adaptive chart is compared with various adaptive charts such as variable sample size VSS variable sampling interval VSI variable sample size and sampling interval VSSI and special variable sample size and sampling interval SVSSI overlinex control chart It is shown that the proposed chart always outperforms SS VSI VSS and VSSI schemes It also can detect shift of size 025 standard deviation quicker than SVSSI scheme Finally the optimal parameters of the proposed chart are recommended
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