Rectifying Inspection of Lots

Abstract

The problem discussed is how to choose a plan of rectifying inspection for a lot or sequence of lots. The purpose of the inspection is minimization of total costs. Three types of inspection plan are considered, namely, no inspection at all, 100 per cent inspection, and sampling inspection according to a sequential plan with linear boundary. Under certain assumptions, it is shown that a near-optimum plan can easily be found. When a single cost factor k, defining the break-even quality, has been determined, the plan may be written down at once, according to a procedure given at the end of §3. It is suggested that for practical purposes there would be little to be gained by refining the procedure, because of vagueness in the data of the problem. The sequential plan is compared with single sampling. A subtle economic and legal problem concerned with the testing of electric meters is discussed at some length. This paper is similar in purpose to a previous paper [1] dealing with inspection of a continuous output.