John, What you are saying is that any conclusion I can make from summary.aov (for instance, to answer a question if physician is a significant variable) will not be correct ?
--- John Fox <[EMAIL PROTECTED]> wrote: > Dear Spencer and Alexander, > > In this case, physician is apparently a factor with > three levels, so > summary.aov() gives you a sequential ANOVA, > equivalent to what you'd get > from anova(). There no simple relationship between > the F-statistic for > physician, which has 2 df in the numerator, and the > two t's. (By the way, I > doubt whether a sequential ANOVA is what's wanted > here.) > > Regards, > John > > At 09:17 AM 12/6/2003 -0800, Spencer Graves wrote: > > The square of a Student's t with "df" degrees > of freedom is an F > > distribution with 1 and "df" degrees of freedom. > > hope this helps. spencer graves > > > >Alexander Sirotkin [at Yahoo] wrote: > > > >>I have a simple linear model (fitted with lm()) > with 2 > >>independant > >>variables : one categorical and one integer. > >> > >>When I run summary.lm() on this model, I get a > >>standard linear > >>regression summary (in which one categorical > variable > >>has to be > >>converted into many indicator variables) which > looks > >>like : > >> > >> Estimate Std. Error t value Pr(>|t|) > >>(Intercept) -3595.3 2767.1 -1.299 0.2005 > >>physicianB 802.0 2289.5 0.350 0.7277 > >>physicianC 4906.8 2419.8 2.028 0.0485 * > >>severity 7554.4 906.3 8.336 1.12e-10 > *** > >> > >>and when I run summary.aov() I get similar ANOVA > table > >>: > >> Df Sum Sq Mean Sq F value > Pr(>F) > >>physician 2 294559803 147279901 3.3557 > 0.04381 > >>* > >>severity 1 3049694210 3049694210 69.4864 > 1.124e-10 > >>*** > >>Residuals 45 1975007569 43889057 > >> > >>What is absolutely unclear to me is how F-value > and > >>Pr(>F) for the > >>categorical "physician" variable of the > summary.aov() > >>is calculated > >>from the t-value of the summary.lm() table. > >> > >>I looked at the summary.aov() source code but > still > >>could not figure > >>it. > >> > >>Thanks a lot. > >> > >>__________________________________ > >> > >> > >>______________________________________________ > >>[EMAIL PROTECTED] mailing list > >>https://www.stat.math.ethz.ch/mailman/listinfo/r-help > >> > > > >______________________________________________ > >[EMAIL PROTECTED] mailing list > >https://www.stat.math.ethz.ch/mailman/listinfo/r-help > > ----------------------------------------------------- > John Fox > Department of Sociology > McMaster University > Hamilton, Ontario, Canada L8S 4M4 > email: [EMAIL PROTECTED] > phone: 905-525-9140x23604 > web: www.socsci.mcmaster.ca/jfox > ----------------------------------------------------- > ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
