The interpretation of the frequencies, mip in the cross-classification given in Table 1.1 is straightforward. Cell 11 displays the number of instances in which both Rater A and Rater B used Category 1. Cell 12 contains the number of instances in which Rater A used Category 1 and Rater B used Category 2, and so forth. The cells with indexes i =j display the numbers of incidences in which the two raters used the same category. These cells are also called the agreement cells. These cells are shaded in Table 1.1.