RES and WRES

From: "Leonid Gibiansky" leonidg@metrumrg.com Subject: [NMusers] RES and WRES Date: Fri, May 27, 2005 3:47 pm My understanding was that WRES (weighted residuals) are obtained from RES (residuals) by some transformation (below is the description from the NONMEM html help) that is roughly equivalent to the division by a variance. To my surprise, I found out that for some observations RES and WRES have different signs (METHOD=1, INTERACTION, combined error model implemented in log-transformed variables Y=F + SQRT(THETA(1)+THETA(2)/F**2)*ERR(1) ). So the question is when it happens and what does it mean. Thanks ! Leonid WRES The weighted residuals for an individual are formed by transform- ing the individual's residuals so that under the population model, assuming the true values of the population parameters are given by the estimates of those parameters, all weighted residu- als have unit variance and are uncorrelated. As with the predic- tion and residual, the weights are also computed at eta = 0.