Hi What is the weighting used in the phoenix model? I see the column ‘Weight’ on the Residuals tab of the output, but I don’t see how to change the weighting in the simulation settings. For example I want my weighting to be 1/standard deviation Kathryn
Hi Kathryn, I’ve copied the following from the 'intro to phx" training manual; the exercise where we first introduce the Phoenix engine, I think there is a similar section comparing weighting in the user docs too - Weighting in Phoenix Models Phoenix WinNonlin Classic WinNonlin Additive: C + CEps = Homoscedastic Uniform Multiplicative: C*(1 + CEps) = Constant CV 1/YhatYhat Power: C + CpowerCeps (Yhat)-2power Power = 0.5: C + C0.5CEps = Poisson 1/Yhat Mixed: C + CEps + CCEpsCMixRatio Custom: user-defined C is the predicted concentration, CEps is the residual error, CmixRatio is the ratio of proportional error to additive error. Standard deviations (σ = Stdev(CEps)) are estimated instead of variances (σ 2 = Var(CEps)) for convenient interpretation • Additive Stdev of 0.1 corresponds to the residual variability in the same units as the modeled concentrations (0.1 µg/L for example) • Multiplicative Stdev of .10 corresponds to a 10% CV • Mixed Stdev of 0.1 with CMixRatio of 1.5 means we have an additive component of 0.1 ( µg/L, for example) and a proportional part of 0.1*1.5 = 0.15 = 15% CV Simon.