Standardization of Microchemical Methods and Apparatus

Cooperative Investigation of Precision and Accuracy in Chemical Analysis of Silicate Rocks

“…The patterns of the distributions are rather like those reported by Willits (10), and their asymmetry shows, as did his results, the tendency for a given chemical procedure to give biased results.…”

“…Averages are not indicated in the results; they could have no meaning for the present preliminary results. Likewise tolerance ranges cannot be derived from the data statistically; these determinations are not compared with fixed standards, as are those described by Scribner (6) and by Willits (10). Rather they are like those that Bright described for steel (1); as he said, we cannot derive rigorous limits from them for the differences from "true content," As Wernimont stated, "The precision of a test method cannot be stated as a single number" (9).…”

Guidelines for Interlaboratory Testing Programs

“…Objectives of various cooperative programs may differ a great deal. For example, Willits (21) and Wernimont (20) describe contrasting approaches that have widely different objectives. In one case reported by Willits, a number of laboratories made determinations on two types of samples representing two chemical species and two levels of the ingredient (element), using two basic procedures but with variations of their own choice (equivalent to many methods).…”