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Cite this document
We have heard so much of statistical methods and quality control methods in the past few years, with their expanded use during the war both here and in England, Canada, and Australia, that it has seemed quite appropriate that the A.S.T.M. should arrange for a session on the subject of statistical quality control and its relation to specifications. Over the past 20 yr. there has been developed, largely within American industry, a science of quality control resting in no small measure on the application of statistical methods to the problems of specification, production, and inspection. With the advent of war, tremendous impetus was given to the utilization of these methods that had been so successfully applied in limited fields. First, on request of the War Department, three standards on quality control methods were issued by the American Standards Association in 1941 and 1942. Then in 1942, under the direction of expert consultants called from industry, the Ordnance Department developed and put into effect the first of its new standard inspection procedures based on quality control principles, and trained inspection personnel in the use of these procedures for its acceptance inspections. Before the war ended, practically all technical branches of the armed services were making wide use of scientific acceptance inspection procedures which were instrumental in inducing better control of quality by manufacturers during production. Further, on the production side, quality control training conferences were conducted under the Office of Production Research and Development of the War Production Board, starting in 1942 and continuing throughout the war, in which over 30 intensive 8-day training courses were given on statistical control with the specific objective of aiding war industry in reducing avoidable waste and in improving the level and uniformity of product quality. Out of these courses there grew some 26 local quality control societies, the majority of which, in 1946, formed a new national society, the American Society for Quality Control. In these activities emphasis has been placed primarily on the application of such methods to production and to inspection and testing, but not too much has been heard about their application to specifications. Now, since one of the principal activities of A.S.T.M. is that of writing standard specifications and standard methods of testing, this Symposium seems to be particularly timely. Many of our specifications are comprised essentially of a set of material requirements. Some include material requirements plus inspection and sampling clauses for verifying conformance to these requirements. There is considerable variation in the content of such specifications, perhaps quite rightly so, considering the wide range of materials and products covered, and of conditions of supply. Often within committee there are long discussions which raise more or less general questions as to the form and content of a specification. For example, should material requirements and acceptance requirements be placed in one document, or should the inspection and sampling clauses for verifying conformance be placed in a separate document? Can such clauses be drawn up to serve all situations—the good supplier and the not-so-good; continuous supply and intermittent supply; tests to be made by the purchaser and tests to be made by the manufacturer? What kind of sampling plans are most advantageous where destructive or costly tests impose a sharp limitation on the number of tests? Can we use quality control acceptance procedures by linking together the results of testing for a series of lots or shipments, or are we limited to procedures that consider each lot on its own merits?
Dodge, H. F.
Bell Telephone Laboratories, Inc., New York, N. Y.