A Master of Science thesis in Engineering Systems Management by Emad Aldin Mohammed Abdelkreem Mohammed entitled, “Optimization of P-Chart for Processes with Multiple Assignable Causes and Random Shift”, submitted in May 2020. Thesis advisor is Dr. Mahmoud Awad. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form).
Attribute control charts are used extensively in many industries to detect assignable causes for many processes. They are particularly useful in the service industries due to difficulty of evaluating services using variable scale. In addition, several critical-toquality characteristics in manufacturing and service can be combined to determine whether to accept or reject the product. The optimization of fraction non-conforming p-chart has been mainly addressed from either statistical or economic prospective or considering only single assignable cause. In this research, we propose an economicstatistical model that considers the process history of the nonconforming units to design a p-chart for processes with multiple assignable causes. The method is demonstrated using a drinking water bottling case and shows improved results compared to existing methods. When comparing the results of the proposed method with traditional methods, the proposed method is expected to reduce poor quality cost by 0.86% per unit. For a mass production company such as the water bottling company with half a million bottles filled every day, the proposed method is expected to provide significant monetary savings along with improved reputation.