STUDY ON VARIABLE SAMPLE SIZE AND SAMPLING INTERVALS Q CONTROL CHART

摘要

In order to better solve product quality control problems without sufficient data, the quality control chart of Variable Sample Size and Sampling Intervals Q (VSSIQ) which combined Q control charts with Variable Sample Size and Variable Sampling Intervals technologies is established on the basic idea of Variable Sampling Intervals (VSI) control chart. Assuming that the amount of time the process in control has negative exponential distribution, the amended average time of signal (AATS) and the average number of samples size (ANSS) can be calculated with Markov Chain model. The result is average chain length parameters of VSSIQ control chart. Combining with an instance, VSSIQ control chart is compared with conventional chart and Variable Sampling Intervals （VSIQ) control chart. The result indicates that VSSIQ control chart can be used to control process even without sufficient sampling data. Furthermore, it may be used to quickly discover variation and effectively diminish defective unit when mean shifts occurs.