Monitoring number of non-conforming items based on multiple dependent state repetitive sampling under truncated life tests

Abstract

In this study, an attribute np control chart based on multiple dependent state repetitive sampling is proposed for monitoring the lifetime of the products since the lifetime of the products is considered as an important quality characteristic of many production processes. It is assumed that the lifetime of the product follows any one of the three lifetime distributions namely Weibull distribution, gamma distribution, and Pareto distribution of second kind with known shape parameter. The proposed chart is based on two pairs of control limits that utilize past subgroup information some times in addition to the current samples’ information under time truncated life test. The performance of the proposed chart is assessed by using out-of-control average run length. In order to get specific average run length, the optimal values of the parameters are determined by using a search procedure. A real time example is provided to assess the performance of the proposed chart. Moreover, performance of the proposed chart is compared with the control chart designed under single sampling procedure by using out-of-control average run length.