The mean of group1 is 0.75,just the same as intercept. Acturally,R treated group1 as reference,so intercept is just group1.
2011/8/16 Jeff Newmiller <jdnew...@dcn.davis.ca.us> > Why would you assert that the mean is the same as the intercept? For data > clustered far from the y axis this seems clearly unlikely to be true. > --------------------------------------------------------------------------- > Jeff Newmiller The ..... ..... Go Live... > DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... > Live: OO#.. Dead: OO#.. Playing > Research Engineer (Solar/Batteries O.O#. #.O#. with > /Software/Embedded Controllers) .OO#. .OO#. rocks...1k > --------------------------------------------------------------------------- > > Sent from my phone. Please excuse my brevity. > > Lao Meng <laomen...@gmail.com> wrote: > >> Hi all: >> I have a question about lm on t-test. >> >> data(sleep) >> >> I wanna perform t-test to test the difference between the 2 groups: >> >> I can use: >> t.test(extra~group) >> >> The t.test result shows that:t = -1.8608; mean1=0.75,mean2=2.33 >> >> >> But I still wanna use: >> summary(lm(extra~group)) >> >> Intercept=0.75,which is mean1,just the same as t.test. >> group2=1.58 means the difference of the 2 groups,so >> mean2=1.58+0.75=2.33,just the same as t.test. >> And some parameters of group2(t value,Pr) are the same as t.test,since >> group2 is the difference of the 2 groups. >> >> My question is: >> How the "t value" of Intercept(group1 acturally) is calculated? >> >> >> Thanks a lot. >> >> My best >> >> [[alternative HTML version deleted]] >> >> ------------------------------ >> >> R-help@r-project.org mailing list >> 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 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.
