Re: Poor PRED estimates

From:Mats Karlsson Subject: Re: [NMusers] Poor PRED estimates Date: Fri, 23 May 2003 06:04:35 +0200 Dear Justin, One possibility is that there is nothing wrong at all with your fit. If you have no covariates in your model, you would expect the plot you describe. There should always be observed concentrations higher than PRED. The question is whether PRED is giving unbiased predictions of you observed data. As a rough guide, if you plot DV versus PRED (or log(DV) versus log(PRED) is your data spans several magnitudes) a regression line should have a slope close to unity. As IPRED looks good, you can also inspect if all your etas are centered around zero (which they should be). Best regards, Mats