Gang Chen wrote: > Thanks a lot for clarification! I just started to learn programming in > R for a week, and wanted to try a simple mixed design of balanced > ANOVA with a between-subject factor > (Grp) and a within-subject factor (Rsp), but I'm not sure whether I'm > modeling the data correctly with either of the command lines. > > Here is the result. Any help would be highly appreciated. > > > fit.lme <- lme(Beta ~ Grp*Rsp, random = ~1|Subj, Model); > > summary(fit.lme) > Linear mixed-effects model fit by REML > Data: Model > AIC BIC logLik > 233.732 251.9454 -108.8660 > > Random effects: > Formula: ~1 | Subj > (Intercept) Residual > StdDev: 1.800246 0.3779612 > > Fixed effects: Beta ~ Grp * Rsp > Value Std.Error DF t-value p-value > (Intercept) 1.1551502 0.5101839 36 2.2641837 0.0297 > GrpB -1.1561248 0.7215090 36 -1.6023706 0.1178 > GrpC -1.2345321 0.7215090 36 -1.7110417 0.0957 > RspB -0.0563077 0.1482486 36 -0.3798196 0.7063 > GrpB:RspB -0.3739339 0.2096551 36 -1.7835665 0.0829 > GrpC:RspB 0.3452539 0.2096551 36 1.6467705 0.1083 > Correlation: > (Intr) GrpB GrpC RspB GrB:RB > GrpB -0.707 > GrpC -0.707 0.500 > RspB -0.145 0.103 0.103 > GrpB:RspB 0.103 -0.145 -0.073 -0.707 > GrpC:RspB 0.103 -0.073 -0.145 -0.707 0.500 > > Standardized Within-Group Residuals: > Min Q1 Med Q3 Max > -1.72266114 -0.41242552 0.02994094 0.41348767 1.72323563 > > Number of Observations: 78 > Number of Groups: 39 > > > fit.aov <- aov(Beta ~ Rsp*Grp+Error(Subj/Rsp)+Grp, Model); > > fit.aov > > Call: > aov(formula = Beta ~ Rsp * Grp + Error(Subj/Rsp) + Grp, data = Model) > > Grand Mean: 0.3253307 > > Stratum 1: Subj > > Terms: > Grp > Sum of Squares 5.191404 > Deg. of Freedom 1 > > 1 out of 2 effects not estimable > Estimated effects are balanced > > Stratum 2: Subj:Rsp > > Terms: > Rsp > Sum of Squares 7.060585e-05 > Deg. of Freedom 1 > > 2 out of 3 effects not estimable > Estimated effects are balanced > > Stratum 3: Within > > Terms: > Rsp Grp Rsp:Grp Residuals > Sum of Squares 0.33428 36.96518 1.50105 227.49594 > Deg. of Freedom 1 2 2 70 > > Residual standard error: 1.802760 > Estimated effects may be unbalanced > This looks odd. It is a standard split-plot layout, right? 3 groups of 13 subjects, each measured with two kinds of Rsp = 3x13x2 = 78 observations.
In that case you shouldn't see the same effect allocated to multiple error strata. I suspect you forgot to declare Subj as factor. Also: summary(fit.aov) is nicer, and anova(fit.lme) should be informative. ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.