Symmetry of gamma distribution data about the mean after processing with EWMA function.
Mohammad M Hamasha1, Mohammed S Obeidat2, Khalid Alzoubi2
1Department of Industrial Engineering, Faculty of Engineering, The Hashemite University, P.O.Box 330127, Zarqa, 13133, Jordan. mhamasha@hu.edu.jo.
Scientific Reports
|September 12, 2023
Summary
Statistical Process Control (SPC) using the Exponentially Weighted Moving Average (EWMA) chart effectively monitors manufacturing quality. This study evaluates EWMA parameters
Area of Science:
- Industrial Engineering
- Statistical Quality Control
- Manufacturing Systems
Background:
- Statistical Process Control (SPC) is crucial for manufacturing quality and variability reduction.
- The Exponentially Weighted Moving Average (EWMA) control chart is effective for detecting small process shifts and ensuring product consistency.
- A key concern with EWMA charts is data asymmetry, which can affect control limit accuracy.
Purpose of the Study:
- To evaluate the impact of EWMA parameters on EWMA control chart performance.
- To assess the reduction of skewness and kurtosis in Gamma-distributed data after EWMA processing.
- To investigate how EWMA parameters influence the shape of the data distribution.
Main Methods:
- Monte Carlo simulation was used to generate Gamma-distributed data.
- The EWMA function was applied to process the generated data.
- Skewness and kurtosis of the data were assessed before and after EWMA processing.
Main Results:
- EWMA processing can reduce data skewness and kurtosis, but may not fully resolve asymmetry issues.
- EWMA parameters significantly influence the degree of skewness and kurtosis reduction.
- The study identified optimal EWMA parameters for improved control chart performance with asymmetric data.
Conclusions:
- EWMA control charts are valuable for quality monitoring, but parameter selection is critical for asymmetric data.
- Understanding the effect of EWMA parameters on data distribution shape is essential for accurate process control.
- This research provides guidance for selecting appropriate EWMA parameters to enhance the reliability of control charts in manufacturing.
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