ABSTRACT
Any manufactured product or service by the production process has a certain zone in quality. If the company works without improving quality, its quality tends to become poor, and sometimes the company has to increase costs of the poor-quality products. This sporadic increase occurs when there are defective products entering the market. The more the sporadic increases in cost of poor quality, the lower the average product quality. Note that at the beginning of operation, cost level of poor quality is at level 20 and fluctuates over time. Over time, the fluctuation increases negatively. It means that the cost of poor quality becomes greater when there is fluctuation. Obviously, if the quality improvement is only implemented once, the costs of poor quality rise will re-occur. In the long run, the costs of poor quality may return to level 20 even though it is not as fast as before. Therefore, to prevent the rising trends, there must be continuous quality improvement.
