The parametrisation is different. The intercept in model 1 is the effect of the "average" subject at days == 0. The intercept in model 2 is the effect of the first subject at days == 0.
ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance Kliniekstraat 25 1070 Anderlecht Belgium To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey 2016-07-12 15:35 GMT+02:00 Utkarsh Singhal <utkarsh....@gmail.com>: > Hi experts, > > While the slope is coming out to be identical in the two methods below, the > intercepts are not. As far as I understand, both are formulations are > identical in the sense that these are asking for a slope corresponding to > 'Days' and a separate intercept term for each Subject. > > # Model-1 > library(lmer) > coef(lmer(Reaction ~ Days + (1| Subject), sleepstudy)) > > # Model-2 > coef(lm(Reaction ~ Days + Subject, sleepstudy)) > > Can somebody tell me the reason? Are the above formulations actually > different or is it due to different optimization method used? > > Thank you. > > Utkarsh Singhal > 91.96508.54333 > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
