26 - Precision and Accuracy: Introduction to Analysis of Variance

Abstract

This chapter introduces the analysis of variance (ANOVA) to achieve greater precision and accuracy in results. ANOVA actually consists of a whole slew of variations of related techniques. The simplest of those variations is considered in the chapter. This technique allows the specification of a set of measurements to be made and a means of analyzing those measurements that will allow not only to unambiguously define the two terms “precision” and “accuracy,” but also in addition compute values for them, and furthermore allow telling if the “accuracy” is worse than the “precision,” or can be accounted for solely by it. The basis of ANOVA, as it is the basis of all the variations on the theme of ANOVA, is the partitioning of the sums of squares. The differences among the various types of ANOVA result mainly from the nature of the experimental design used, which in turn determines which sums of squares can be calculated. ANOVA calculations were first utilized in agricultural work to determine the effects of various fertilizer treatments or other growth conditions on crop test plots. In biology and medicine, the use of ANOVA has become popular in the determination of the effectiveness of different drugs on human or animal test populations, and of an antibiotic on suspensions of pathogenic bacteria.