“…Markers whose association with the outcome lies between independence and comonotonicity are expected to exhibit useful discriminative and predictive properties. A way to quantify the association within ( M , T ), and consequently within ( M , D ), can be achieved by using Kendall's coefficient of concordance, tau, which is defined as 31 where ( m , t ) ∈ (− ∞ , ∞ ) 2 and cor( X , Y ) is the correlation coefficient between the random variables X and Y ; here, the random vectors ( M 1 , T 1 ) and ( M 2 , T 2 ) are independent copies of ( M , T ). Kendall's tau is a popular nonparametric measure of ordinal association between M and T .…”