Getting Sphericity Tests for Within Subject Repeated Measure Anova (using "car" package) (Adjusted Dataset)
Dear Segios, For repeated-measures designs, the Anova() function requires a multivariate linear model fit to the "wide" version of the data set, in which each of the repeated measures appears as a separate variable. It is necessary that you have the same occasions observed for all subjects. For your scaled-down example, you'd have two response variables named, e.g., Sessn1 and Sessn2. Then you'd fit the multivariate linear model as mod <- lm(cbind(Sessn1, Sessn2) ~ Trtmnt, data=Dataset). The idata data frame could simply be idata <- data.frame(Sessn=factor(1:2)). Then you could get the MANOVA and repeated-measure ANOVA, including sphericity test, etc., as summary(Anova(mod, idata=idata, idesign=~Sessn)). I hope this helps, John -------------------------------- John Fox Senator William McMaster Professor of Social Statistics Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox
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On
Behalf Of Sergios (Sergey) Charntikov Sent: November-09-09 1:18 PM To: r-help at r-project.org Subject: [R] Getting Sphericity Tests for Within Subject Repeated Measure Anova (using "car" package) (Adjusted Dataset) [corrected dataset below] Hello everyone, I am trying to do within subjects repeated measures anova followed by the test of sphericity (sample dataset below). I am able to get either mixed model or linear model anova and TukeyHSD,
but
have no luck with Repeated-Measures Assuming Sphericity or Separate Sphericity Tests. I am trying to follow example from "car" package, but it seems that I am
not
getting something right.
Dataset$Sessn <- as.factor(Dataset$Sessn)
LinearModel.1 <- lm(Response ~ Sessn*Trtmt, data=Dataset)
summary(LinearModel.1)
All, good so far, but I have problem understanding "idata=" and "idesign=" functions pertaining to my example. Session is my repeated measure (Sessn
1
and Sessn 2 = two sessions, in reality I have more) and it is already stacked. Any help or guidance on this matter. Thank you, my mock dataset is below. Each subject has two levels of treatment throughout four calendar days which are recoded to Session 1 and Session 2 in order to compare treatments by the first and subsequent days
of
exposure (Treatment x Session; my DV is Response; Session is repeated). Subj Trtmt Sessn Response 1 N 1 5 1 D 1 6 1 N 2 4 1 D 2 7 2 N 1 8 2 D 1 9 2 N 2 2 2 D 2 1 3 N 1 4 3 D 1 5 3 N 2 6 3 D 2 2 4 N 1 5 4 D 1 6 4 N 2 4 4 D 2 7 5 N 1 8 5 D 1 9 5 N 2 2 5 D 2 1 6 N 1 4 6 D 1 5 6 N 2 6 6 D 2 2 Sincerely, Sergios Charntikov (Sergey), MA Behavioral Neuropharmacology Lab Department of Psychology University of Nebraska-Lincoln Lincoln, NE 68588-0308 USA sergioschr-at-gmail-dot-com [[alternative HTML version deleted]]
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