A case study on measuring inspection performance for inspection job design

In the quality control system, most of the information for decision making and problem solving can be obtained by inspection activities. Therefore, the inspection work should be organized to maximize meeting the quality objectives. It has already been publicized that data obtained from measurement of inspection performance will supply an effective basis for assessment and design of the inspection station and inspection job. This paper is intended to report on a case study of measurement of inspection performance conducted for the assessment and design of an inspection job in a manufacturing company. Quality control specialists selected three groups of items having representative deficiencies under routine inspection, inspected as inspection job samples. They had individual inspectors inspect each sample to obtain data consisting of the rate of defects detected out of all the defects, and the proportion of erroneous findings in the total number of findings by each inspector. Thus they identified many problems in the inspection job to be corrected to enhance the inspection accuracy. Appropriate action was taken to remedy the situation. In the first place, the inspection job was redesigned. In the second, the method of training inspectors was reviewed and modified. As a result, the probability of defects passing the inspection undetected was greatly reduced.