A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand

Thesis (M.Eng.) - Asian Institute of Technology, 1977

This study investigates the relationship between operator fatigue and quality deterioration. Based on t he data collected from a selected factory, it is found that a straight line is the best fit for the relationship. The finding is incorporated in the design of economic quality control chart models for a mass production man-machine process. As a matter of fact, the process may go out of control because of the machine errors or the human errors due to fatigue. If it is a machine error, t he machine can be readjusted. The human fatigue continuously increases the risk of false indication by the control chart. Model s formulated in this study are based on a trade off between the two types of risks involved: (a) indication of a shift in the process when non has taken place and (b) failure to indicate a shift when one has really occurred. Models are developed for attributes and variables control charts to minimize the total cost given by a set of optimal parameters the sample size; the multiple of standard deviation which determines the spread of control limits; and the sampling frequency. Data from a factory has been used to test the applicability of the models .