On 6 Mar 2003 at 10:38, rob foxall (IFR) wrote: You can use linear.hypothesis() from the package car (on CRAN).
Kjetil Halvorsen > Hello all, > > A really noddy question for you all: I'm trying without success to do > some subhypothesis testing. Using simple anova model, with a toy dataset from a > book. I have four factors A,B,C,D, and wish to test mu_C = mu_D. This is what I have > tried: > > > > > contrasts(infants$group,how.many=1) <- c(0,0,1,-1) > > > contrasts(infants$group) > > [,1] > > A 0 > > B 0 > > C 1 > > D -1 > > > fit <- aov(age~group,data=infants) > > > summary(fit) > > Df Sum Sq Mean Sq F value Pr(>F) > > group 1 0.740 0.740 0.2693 0.6092 > > Residuals 21 57.727 2.749 > > > > Now I know from the book, hand calculations and SPSS that for "group", Sum Sq = Mean > Sq = 1.12, not 0.740. Also from the standard anova: > > > > > contrasts(infants$group) <- "contr.treatment" > > > fit <- aov(age~group,data=infants) > > > summary(fit) > > Df Sum Sq Mean Sq F value Pr(>F) > > group 3 14.778 4.926 2.1422 0.1285 > > Residuals 19 43.690 2.299 > > > > So I'd like to have the (correct) Mean Sq value divided by 2.299 and not 2.749, with > 19 and not 21 df. Any advice on how to correctly use contrasts for subhypothesis > testing, including where to find it in the manuals, would be much appreciated. > > > > Cheers, > > Rob. > > > > (Other info) > > > > Using R 1.6.2, windows xp, > > > > data: > > > infants > > group age > > 1 A 9.00 > > 2 A 9.50 > > 3 A 9.75 > > 4 A 10.00 > > 5 A 13.00 > > 6 A 9.50 > > 7 B 11.00 > > 8 B 10.00 > > 9 B 10.00 > > 10 B 11.75 > > 11 B 10.50 > > 12 B 15.00 > > 13 C 11.50 > > 14 C 12.00 > > 15 C 9.00 > > 16 C 11.50 > > 17 C 13.25 > > 18 C 13.00 > > 19 D 13.25 > > 20 D 11.50 > > 21 D 12.00 > > 22 D 13.50 > > 23 D 11.50 > > > [[alternate HTML version deleted]] > > ______________________________________________ > [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
