I have a problem getting the lmer function of the lme4 package to use the appropriate degrees of freedom for testing. Consider the Semiconductor data from the SASmixed package: library(SASmixed) Semi.lme <- lme(resistance ~ ET * position, random=~1|Grp, data=Semiconductor) anova(Semi.lme) numDF denDF F-value p-value (Intercept) 1 24 3237.261 <.0001 ET 3 8 1.942 0.2015 position 3 24 3.385 0.0345 ET:position 9 24 0.809 0.6125 Here, the ET effect is (correctly) tested on 8 denominator degrees of freedom. In the example in the SASmixed package, the following code is presented: (fm1Semi <- lmer(resistance ~ ET * position + (1|Grp), Semiconductor)) anova(fm1Semi) Analysis of Variance Table Df Sum Sq Mean Sq Denom F value Pr(>F) ET 3 0.647 0.216 32.000 1.9415 0.14273 position 3 1.129 0.376 32.000 3.3855 0.02991 * ET:position 9 0.809 0.090 32.000 0.8092 0.61127 So here, all effects are tested with 32 denominator degrees of freedom. I have looked at the help page for lmer but have been unable to figure out how to specify the hierarchical structure of a split plot experiment. Also, I have Googled but without any luck. Any help will be appreciated. Søren
______________________________________________ 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