EWMA control charts with variable sample sizes and variable sampling intervals

摘要

Traditional control charts for process monitoring based on taking samples of fixed size from the process using a fixed sampling interval. Variable Sample Size (VSS) and Variable Sampling Interval (VSI) control charts vary the sampling rate from the process as a function of the data from the process. VSS and VSI control charts sample at a higher rate when there is evidence of change in the process, and are thus able to detect process changes faster than traditional control charts.