Introduction

This chapter describes the basic fourfold, 2 × 2, contingency tableContingency table, cross-classifying actual and predicted classes, and introduces various notations (literal, algebraic, probability, error) which will be used to define various measures derived from the 2 × 2 table which are described in the subsequent chapters. It also considers prevalencePrevalence rate, level of test (positive and negative sign rates), and the setting of decision thresholds or cut-offs.