Alex Baugh wrote: > I am executing a Repeated Measures Analysis of Variance with 1 DV (LOCOMOTOR > RESPONSE), 2 Within-Subjects Factors (AGE, ACOUSTIC CONDITION), and 1 > Between-Subjects Factor (SEX). > > Does anyone know whether the between-subjects factor (SEX) belongs in the > Error Term of the aov or not? And if it does belong, where in the Error Term > does it go? The 3 possible scenarios are listed below: > > > > e.g., > > 1. Omit Sex from the Error Term: > > >> My.aov = aov(Locomotor.Response~(Age*AcousticCond*Sex) + Error >> > (Subject/(Timepoint*Acx.Cond)), data=locomotor.tab) > > note: Placing SEX outside the double paretheses of the Error Term has the > same statistical outcome effect as omitting it all together from the Error > Term (as shown above in #1). > > > > 2. Include SEX inside the Error Term (inside Double parentheses): > > >> My.aov = aov(Locomotor.Response~(Age*AcousticCond*Sex) + Error >> > (Subject/(Timepoint*Acx.Cond+Sex)), data=locomotor.tab) > > > > 3. Include SEX inside the Error Term (inside Single parentheses): > > > >> My.aov = aov(Locomotor.Response~(Age*AcousticCond*Sex) + Error >> > (Subject/(Timepoint*Acx.Cond)+Sex), data=locomotor.tab) > > note: Placing SEX inside the single parentheses (as shown above in #3) > generates no main effect of Sex. Thus, I'm fairly confident that option #3 > is incorrect. > > > > Scenarios 1,2, and 3 yield different results in the aov summary. > > You don't generally want terms with systematic effects to appear as error terms also, so 3 is wrong.
In 2 you basically have a random effect of sex within subject, which is nonsensical since the subjects presumably have only one sex each. This presumably generates an error stratum with 0 DF, which may well be harmless. That leaves 1 as the likely solution. You'll probably do yourself a favour if you learn to expand error terms, a/b == a + a:b, etc.; that's considerably more constructive than trying to think in terms of whether things are inside or outside parentheses. > > Thanks for your help! > > Alex > > > > > > ______________________________________________ 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.