Chi-Squared statistic Cochran-Armitage Chi-Square Statistic for Trend A chi-square statistic used to test whether a dichotomous variable and an ordinal variable are related. The statistic is calculated using a weighted sum of the differences between observed and expected frequencies, where the weights are based on the scores assigned to the ordered categories. Mathematically, it's often expressed as: Z = ∑(wi(Oi-Ei)/sqr( wi^2.Ei(1-Ei)) where wi are the scores, Oi observed frequencies, and Ei expected frequencies. Cochran, W. G., & Armitage, P. (1954). The χ² Test for Trend. Biometrika, 41(1-2), 171–178. SEVCO & STATO Kenneth Wilkins, Brian S. Alper, Joanne Dehnbostel Philippe Rocca-Serra ready for release