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.
Thanks for your help!
Alex
--
Alexander T Baugh
Institute for Neuroscience
Univ. of Texas at Austin
Austin, TX 78712
512.475.6164
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