290 H E A L S I 'S TRM TECH.X I CA L JO URN A L 



of the same piece of cloth, and in order to measure the effect of the treatments 

 the tests are repeated systematically so that the variations are 'averaged out.' 

 Some of the natural variation, however, is systematic, and by adopting a 'Latin 

 Square' arrangement of treatments on the cloth (such as is much used in agri- 

 cultural yield trials), these systematic variations are eliminated from the com- 

 parison, and in the instance quoted the result was to reduce by one-half the 

 number of tests necessary for a given significance as compared with a random 

 arrangement."^ 



To the extent to which biology becomes an important element in indus- 

 trial research — and it would appear to be on the point of doing so in such 

 fields as food manufacturing — it can be expected that the type of statistical 

 work listed under (a) and (6) will rapidly increase. 



(c) In laying out an inspection routine. Manufacturing inspection 

 frequently yields data which are best interpreted statistically, either 

 because only spot-checks are taken, or because the method of inspection 

 gives measurements which are themselves subject to accidental fluctuation. 

 In such cases statistical theory is of great advantage in setting up an 

 effective and economical inspection program. It is being so used in certain 

 industries, notably in electrical manufacturing and textiles, but the poten- 

 tial field of usefulness is far from covered. 



The following example is quoted from an address by Mr. Warner Eustis, 

 Staff Ofiicer on Research of the Kendall Company: 



"Surgical sutures are twisted strands of sheep intestine, which has been slit 

 lengthwise. . . . After a stated number of days a sewing with such material, im- 

 planted in the body during a surgical operation, will be digested and disappear 

 as the healing processes progressively take up the load originally held by the 

 suture. . . . Here is a product which it is impossible to test in any way without 

 destroying the product, especially as each suture is sealed in an individual, steri- 

 lized tube. Our final product tests must all be conducted by breaking open a 

 sterile tube and testing the product therein. The quahty appraisal of such a 

 product naturally rests upon probability, rather than upon an actual testing of 

 each item. Due to the nature of such a product, in which a single failure may 

 destroy human life, the need for accurate quality appraisal is superlative."^ 



{d) In the control of manufacturing processes. Inspection is not merely 

 a means of discarding bad product; it is also a means of detecting trouble 

 in the factory. This is obvious in the extreme cases when the product is 



^ "The Application of Statistical Methods to Production and Research in Industry," 

 by R. H. Pickard, Supplement to the Journal of the Royal Statistical Society, Vol. 1, 

 No. 2, 1934, pp. 9-10. 



' "Why the Kendall Company is interested in Statistical Methods," by Warner Eustis, 

 Proceedings of the Industrial Statistics Conference held at M. I. T., Cambridge, Mass., 

 Sept. 8-9, 1938, pp. CXLIII-CXLIV, published by Pitman Publishing Corporation. 



