Re: Placebo-corrected PD models

From:Leonid Gibiansky Subject:Re: [NMusers] Placebo-corrected PD models Date:Fri, 17 May 2002 08:40:04 -0400 Daren, I am not sure that it is correct to compare objective functions in this setting. I would present it as follows: model 1 R1= (...) model 2 (equivalent to R2): R1=(...)+Log(Response(0)/Placebo(0)) Model 2 can be presented as R1=(...)+theta(.)*Log(Response(0)/Placebo(0)) with theta()=1 I would fit these models and compare objective functions, with the understanding that the second model has one extra parameter (even if it is chosen as 1; you may allow optimization of theta(.) instead). Alternatively, you may replace model 2 by R1=(...)+eta() if you have only one response circle (or you will need to implement inter-occasion variability instead of eta(.) if you have many response circles). Again, model has one extra parameter, variance of inter-occasion variability. Leonid