A table for classifying elements of a population according to two variables - recording the relationship between two classes of items, each entry counting the number of specific occurrences of the possible combinations. The rows correspond to one variable and the column to the other. The classes compared in such a cross tabulation might be, for instance, sites in different ecological zones, artifacts in different contexts, or the coincidence of different decorative traits and fabric types in a pottery assemblage. Various statistics can be calculated from such a table, especially to test the significance of the observed correlations; the chi-square test is often used to do this.