Dynamic Sample Size Based EWMA Control Chart Using Piecewise Linear Function

ABSTRACT This work introduces a exponentially weighted moving average (EWMA) control chart that utilizes a piecewise linear function to determine sample sizes adaptively. The traditional methods, which employ fixed sample sizes or simple linear variations, struggle to adjust precisely to process shifts. The newly developed approach increases sensitivity and responsiveness by dynamically adjusting sample sizes based on the EWMA statistic. Comparative analyses with classical EWMA and variable sample size EWMA control charts show that the proposed method significantly enhances the performance of the control chart. The findings of the study prove that the piecewise linear adaptive sample size strategy displays superior sensitivity and efficiency. To demonstrate the usefulness of the proposed control chart, a detailed evaluation of average run length and standard deviation of run length is included, which highlights and explains the effectiveness of the proposed control chart.