A Simple Inspection Scheme for Two Types of Defect

The paper examines a problem in quality inspection for two independent defects, A and B. For defect A, process control is at least as important as product screening. Low-cost, rapid sequential inspection takes place for a run of k consecutive type-A defectives. When this occurs, the production process is halted and, if necessary, adjusted, and the run of k defectives is discarded. The entire pre-run sequence is retained, forming the production run. No type-B defectives are permitted; testing for this type of defect is expensive, so detection is by Dorfman screening of the production run. Features of interest are the choice of k in relation to the average length of a production run and the outgoing proportion defective, the average cost per production run of testing for attribute B, and the average number of items finally accepted per production run.