My apologies to the list for sending this without adequate research. I have found my answer; please ignore! Thanks.
I've been experimenting with drop1 for my biostatistics class, to obtain the so-called Type III sums of squares. I am fully aware of the deficiencies of this method, however I feel that the students should be familiar with it. What I find baffling is that when applied to a fully balanced design, you obtain different sums of squares. I've used this for several years in Splus and R and never encountered this before. Am I off my rocker? I have read the help files and remain clueless. Thanks for any advice. > replications(Wt~Sex*Par.trt, data=tmp1) $Sex [1] 22 $Par.trt [1] 22 $"Sex:Par.trt" Par.trt Sex N S F 11 11 M 11 11 > summary(tmp2<-aov(Wt~Sex*Par.trt, data=tmp1)) Df Sum Sq Mean Sq F value Pr(>F) Sex 1 215600 215600 31.5367 1.638e-06 *** Par.trt 1 7127 7127 1.0425 0.3134 Sex:Par.trt 1 19236 19236 2.8138 0.1013 Residuals 40 273459 6836 --- Signif. codes: 0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 > drop1(tmp2, ~., test="F") Single term deletions Model: Wt ~ Sex * Par.trt Df Sum of Sq RSS AIC F value Pr(F) <none> 273459 392 Sex 1 53018 326477 398 7.7552 0.008144 ** Par.trt 1 1473 274932 391 0.2154 0.645067 Sex:Par.trt 1 19236 292695 393 2.8138 0.101256 --- Signif. codes: 0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 > ================================================================== George W. Gilchrist Email #1: [EMAIL PROTECTED] Department of Biology, Box 8795 Email #2: [EMAIL PROTECTED] College of William & Mary Phone: (757) 221-7751 Williamsburg, VA 23187-8795 Fax: (757) 221-6483 http://gwgilc.people.wm.edu/ ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html