## Quick Reference

A non-parametric test for comparing two survival curves, which results from the work of Sir David Cox and Nathan Mantel. Denote the total number of deaths in the second group by *D*_{2}, and let the ordered survival times of the combined group be *t*_{(1)}<*t*_{(2)}<…<*t*_{(k)}. The test statistic, *C*, is given by C = U / √*I*, where , , and *m*_{(j)} is the number of survival times equal to *t*_{(j)}, *d*_{(j)} is the total number of individuals who died (or were censored) at time *t*_{(j)}, and *p*_{(j)} is the proportion of these who were in the second group. If the differences between the survival curves are attributable to random variation then *C* has a standard normal distribution.

*Subjects:*
Probability and Statistics.