Repeated measures data occur when more than one measurement is collected on the same unit (e.g. subject). Use this tag for RM-ANOVA together with [anova] tag.
Questions tagged [repeated-measures]
2455 questions
107
votes
2 answers
What is covariance in plain language?
What is covariance in plain language and how is it linked to the terms dependence, correlation and variance-covariance structure with respect to repeated-measures designs?
abc
- 1,747
- 3
- 17
- 32
52
votes
2 answers
Using lmer for repeated-measures linear mixed-effect model
EDIT 2: I originally thought I needed to run a two-factor ANOVA with repeated measures on one factor, but I now think a linear mixed-effect model will work better for my data. I think I nearly know what needs to happen, but am still confused by few…
phosphorelated
- 743
- 2
- 7
- 9
44
votes
8 answers
Is it valid to include a baseline measure as control variable when testing the effect of an independent variable on change scores?
I am attempting to run an OLS regression:
DV: Change in weight over a year (initial weight - end weight)
IV: Whether or not you exercise.
However, it seems reasonable that heavier people will lose more weight per unit of exercise than thinner…
ChrisStata
- 581
- 1
- 6
- 7
36
votes
1 answer
Multiple comparisons on a mixed effects model
I am trying to analyse some data using a mixed effect model. The data I collected represent the weight of some young animals of different genotype over time.
I am using the approach proposed…
nico
- 4,246
- 3
- 28
- 42
32
votes
5 answers
Modelling longitudinal data where the effect of time varies in functional form between individuals
Context:
Imagine you had a longitudinal study which measured a dependent variable (DV) once a week for 20 weeks on 200 participants. Although I'm interested in general, typical DVs that I'm thinking of include job performance following hire or…
Jeromy Anglim
- 42,044
- 23
- 146
- 250
29
votes
3 answers
Differences between MANOVA and Repeated Measures ANOVA?
What is the difference between a repeated measures ANOVA over some factor (say experimental condition) and a MANOVA?
In particular one website I stumbled across suggested that MANOVA does not make the same assumption of sphericity that repeated…
russellpierce
- 17,079
- 16
- 67
- 98
27
votes
5 answers
Example reports for mixed-model analysis using lmer in biology, psychology and medicine?
As the general consensus seems to be to use mixed-models via lmer() in R instead of classical ANOVA (for the often cited reasons, like unbalanced designs, crossed random effects etc.), I would like to give it a try with my data. However I am worried…
jokel
- 2,403
- 4
- 32
- 40
26
votes
2 answers
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.
aov(Y ~ B + Error(A/B), data=d)
Below analogous mixed…
amoeba
- 93,463
- 28
- 275
- 317
26
votes
3 answers
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)
What syntax in R can be used to perform a post hoc test after an ANOVA with repeated…
L_T
- 1,463
- 7
- 20
- 25
24
votes
2 answers
Why do lme and aov return different results for repeated measures ANOVA in R?
I am trying to move from using the ez package to lme for repeated measures ANOVA (as I hope I will be able to use custom contrasts on with lme).
Following the advice from this blog post I was able to set up the same model using both aov (as does ez,…
Henrik
- 13,314
- 9
- 63
- 123
23
votes
2 answers
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 measures ANOVAs. I've done this for a single-factor repeated measures experiment and for a two-factor experiment with one between-subjects factor and one…
mark999
- 3,180
- 2
- 22
- 31
22
votes
3 answers
When is a repeated measures ANOVA preferred over a mixed-effects model?
In response to this question, regarding whether my design where I randomly presented participants with pictures from different categories was an example where I should use a repeated measures ANOVA, I got the answer that I should use a mixed-model…
Speldosa
- 668
- 1
- 7
- 23
22
votes
2 answers
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 package in R as shown below.
#response data from…
bluepole
- 2,376
- 3
- 25
- 34
21
votes
1 answer
Showing that 100 measurements for 5 subjects provide much less information than 5 measurements for 100 subjects
At a conference I overheard the following statement:
100 measurements for 5 subjects provide much less information than 5 measurements for 100 subjects.
It's kind of obvious that this is true, but I was wondering how one could prove it…
DeltaIV
- 15,894
- 4
- 62
- 104
20
votes
5 answers
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 that the likely violation of sphericity in these…
russellpierce
- 17,079
- 16
- 67
- 98