

Comparing models with different varia... 

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Sally Czaja posted on Tuesday, June 20, 2006  12:03 pm



I would like to compare models (using AIC and AIC weights) in which a 2nd and 3rd predictor is added to a base model that has just 1 predictor. I'm confused on how to specify the simpler models. If the base model is "Y on P;" and the 2nd model is "Y on P C;" (C is a control variable), then the base model has a better (lower) AIC and an AIC weight of 1 (i.e., they're not even close), even though the Rsquared is better (higher) in the 2nd model. Should C be in the base model? (if so, how exactly?). The 3rd model introduces a mediator: "Y on P C M;" "M on P C;". If the comparison model is "Y on P C;", then the simpler model is preferred again. I want to make sure I'm doing this right before I interpret these results. Thanks. 


You need to include the full set of variables in each model for the loglikelihood values to be on the same scale. y ON p c m; y ON p c m@0; o ON p c@0 m@0; 

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