157 views

aov() and lme() give completely different results in analyzing repeated measures [duplicate]

I have data consisting of two measures per subject (variable score, measured at Day 0, and Day1 per each subject). There are two groups, and each subject belongs to one of them (variable Group). I ...
19k views

Post-hocs for within subjects tests?

What is the preferred method for for conducting post-hocs for within subjects tests? I've seen published work where Tukey's HSD is employed but a review of Keppel and Maxwell & Delaney suggests ...
26k views

What is compound symmetry in plain english?

I recently realized that a mixed-model with only subject as a random factor and the other factors as fixed factors is equivalent to an ANOVA when setting the correlational structure of the mixed model ...
46k views

Post hoc test after ANOVA with repeated measures using R

I have performed a repeated measures ANOVA in R, as follows: aov_velocity = aov(Velocity ~ Material + Error(Subject/(Material)), data=scrd) summary(aov_velocity) ...
10k views

How to choose random- and fixed-effects structure in linear mixed models?

Consider the following data from a two-way within subjects design: ...
3k views

Big disagreement in the slope estimate when groups are treated as random vs. fixed in a mixed model

I understand that we use random effects (or mixed effects) models when we believe that some model parameter(s) vary randomly across some grouping factor. I have a desire to fit a model where the ...
28k views

Repeated measures ANOVA with lme/lmer in R for two within-subject factors

I'm trying to use lme from the nlme package to replicate results from aov for repeated ...
11k views

Paired t-test as a special case of linear mixed-effect modeling

We know that a paired t-test is just a special case of one-way repeated-measures (or within-subject) ANOVA as well as linear mixed-effect model, which can be demonstrated with lme() function the nlme ...
2k views

Does it make sense for a fixed effect to be nested within a random one, or how to code repeated measures in R (aov and lmer)?

I have been looking through this overview of lm/lmer R formulas by @conjugateprior and got confused by the following entry: Now assume A is random, but B is fixed and B is nested within A. ...
4k views

How to perform a 4 by 4 mixed ANOVA with between- and within-subjects contrasts using R?

Beginner user of R here struggling with a repeated measures ANOVA. I have a dataset that consists of one between subjects factor with 4 levels (coded in a single variable called 'groups'), and one ...
8k views

How to specify specific contrasts for repeated measures ANOVA using car?

I am trying to run a repeated measures Anova in R followed by some specific contrasts on that dataset. I think the correct approach would be to use Anova() from the ...
2k views

Equivalence between a repeated measures anova model and a mixed model: lmer vs lme, and compound symmetry

I have some trouble obtaining equivalent results between an aov between-within repeated measures model and an lmer mixed model. ...
4k views

Conflicting results of summary() and anova() for a mixed model with interactions in lmer+lmerTest

I recently came across what I think may be a problem in how the anova() function from the lmerTest packages computes its F-...