Inspectors' performance and understanding in sheet steel inspection

Three studies were performed to better understand the complex task of sheet steel inspection for multiple surface defects. Their aim was to combine techniques from off-line performance measurement studies with interviews and questionnaires coming from a more holistic tradition of inspection. In this way, more detailed insights were obtained from three studies of nine highly-trained and experienced steel inspectors. The performance study was designed to compare lighting conditions using a visual search task. It did not find lighting differences, but did find other task differences and the typical large individual differences. These individual differences were explored further with detailed interviews, a task analysis and a detailed questionnaire. Areas of significant agreement among inspectors were found, as were responses that differentiated high from low performing inspectors. Rasmussen's skill/rule/ knowledge classification was used to aid the analysis of these latter studies, showing the contribution of higher-level cognitive processes to the inspection task.