The underlying philosophy of the studies was to observe professionally qualified manual inspectors at work in typical inspection tasks, and to note and record the standard of performance achieved and any errors made. The programme included a range of tests of differing types and used special facilities, equipment and observational and recording techniques. The inspection conditions and environment in these facilities were set to typical industrial inspection conditions.

It is concluded that the results support the conclusions of the earlier PISC programme. Inspector variability in calibrating equipment and detecting flaws has been demonstrated and quantified. The flaw detection capabilities of the inspectors studied vary significantly, although all were experienced and professionally qualified to similar levels. This variability is caused in many instances by differences in technical skills, such as scanning and maintaining ultrasonic coupling, but a number of errors arose for other reasons, principally loss of concentration and vigilance arising from tiredness.

The information obtained in the studies should be utilised to assist in the development and specification of precautions against human error.