Tied pair (ordinal data)

Two observations tied on a variable have equal recorded values of that variable. For observations of two ordinal categorical variables, distinguish pairs tied only on the first, only on the second, or on both. Goodman and Kruskal's gamma excludes all such pairs, whereas Somers' D retains ties on the response when measuring directional predictive association. Consequently these coefficients can differ markedly for the same contingency table.