The Performance of Variable Sample Size X¯ Chart with Measurement Errors

The variable sample size (VSS) X¯ chart has been investigated by several researchers under the assumption of no measurement error. However, in practice, measurement errors may exist in quality control applications. In this paper, the overall performance of the VSS X¯ chart is investigated when measurement errors exist using a linearly covariate error model, and a methodology is proposed for choosing optimal parameters by considering measurement errors. It is shown that the overall performance of the VSS X¯ chart is significantly affected by the presence of measurement errors. The effect of taking multiple measurements for each item in a subgroup on the performance of VSS X¯ chart is also investigated in this paper. An example is provided to illustrate the application of the VSS X¯ chart with measurement errors.