An enhanced EWMA chart with variable sampling interval scheme for monitoring the exponential process with estimated parameter

Abstract

Abstract Control charts have been used to monitor product manufacturing processes for decades. The exponential distribution is commonly used to fit data in research related to healthcare and product lifetime. This study proposes an exponentially weighted moving average control chart with a variable sampling interval scheme to monitor the exponential process, denoted as a VSIEWMA-exp chart. The performance measures are investigated using the Markov chain method. In addition, an algorithm to obtain the optimal parameters of the model is proposed. We compared the proposed control chart with other competitors, and the results showed that our proposed method outperformed other competitors. Finally, an illustrative example with the data concerning urinary tract infections is presented.

Keywords

• Exponential process
• Estimated parameter
• Exponentially weighted moving average
• Variable sampling interval
• Markov chain method
• Optimization algorithm design