Proefopzetten in de Industrie

Experimental designs in industry. It is pointed out that in industry owing to the greater speed of modem mass‐production we have a greater need for simple experimental designs than in agriculture. The paper makes a special and extensive study of the simplest of all designs: the two‐way classification. A distinction is made between qualitative and quantitative factors; factors for which we do not, and for which we do know the levels. Three cases must then be distinguished: (1) two qualitative factors, (2) one qualitative and one quantitative factor, and (3) two quantitative factors. To these, different methods of variance analysis must be applied; in (1) the customary analysis according to rows and columns is adequate, but in (2) we can effectively use polynomial regression analysis in one direction, and in (3) we can do so in both directions. Examples of each of these types of analysis are provided. The opinion is expressed that the analysis of variance serves to pick out from among a number of conceivable models, the simplest model that will adequately describe the observations, and further to provide an estimate of the residual fluctuations. The result of an analysis of variance is of no use for technical purposes; the model chosen expressed in the form of a numerical equation is the information to be used in the factory.