Dear All, A friend asked me for help with a regression problem dealing with y and x, both random variables. The x and y are respectively the observed and estimated biomass values of a green algae derived from an ecological model. We first considered it to be a model II regression and derived the intercept and slope using Bartlett's method, reduced major axis (geometric mean regression) and major axis method (as implemented by Legendre). Then the significance and percentage of variance explained by the models was calculated (by hand) through ANOVA or Permutation test/Correlation (for later mehod). Our questions are: using a "special" approach to regression (model II) and then an ANOVA makes sense? I favour Legendre's approach but cannot justiy why! Is there any code/package available dealing with this "problem"? Thanks, Eduardo