Questions tagged [repeated-measures]
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.
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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 ...
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Determining true mean from noisy observations
I have a large set of data points of the form (mean, stdev). I wish to reduce this to a single (better) mean, and a (hopefully) smaller standard deviation.
Clearly I could simply compute $\frac{\sum ...
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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 ...
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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?
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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 ...
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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)
...
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What is the lme4::lmer equivalent of a three-way repeated measures ANOVA?
My question is based on this response which showed which lme4::lmer model corresponds to a two-way repeated measures ANOVA:
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What experimental design is this?
I collect blood from one human (donor), separate leukocytes and put $2\times10^6$ of them per each well of five:
well 1: $2\times10^6$ Lk (leukocytes)
well 2: $2\times10^6$ Lk
well 3: $2\times10^...
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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 ...
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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.
...
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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 ...
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How can I test for differences in variation between groups in a mixed model (lme4)?
I would like to test for differences in variation, not in means, between two sites. By looking at a boxplot of my data I see that bird song in one site look much more variable in length than in ...
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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 ...
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A non-parametric repeated-measures multi-way Anova in R?
The following question is one of those holy grails for me for some time now, I hope someone might be able to offer a good advice.
I wish to perform a non-parametric repeated measures multiway anova ...
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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 ...
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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.
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Repeated measures ANOVA vs. factorial ANOVA with subject factor: understanding "error strata" and Error() term in aov
Consider repeated measures ANOVA (RM-ANOVA) with one within-subject factor A and several measurements per subject for each level of ...
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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 ...
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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 ...
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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 ...
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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 ...
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Equivalence of (0 + factor|group) and (1|group) + (1|group:factor) random effect specifications in case of compound symmetry
Douglas Bates states that the following models are equivalent "if the variance-covariance matrix for the vector-valued random effects has a special form, called compound symmetry" (slide 91 in this ...
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Is a "split plot" ANOVA with two factors the same as two-way ANOVA with repeated measures in one factor?
Is a "split plot" ANOVA with two factors identical to two-way ANOVA with repeated measures in one factor? if not, what is the distinction?
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Is using error bars for means in a within-subjects study wrong?
I seem to recall one of my professors saying that error bars are completely uninformative when comparing repeated measures taken from a single group. Is that true?
Surely many studies compute the ...
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Difference between Repeated measures ANOVA, ANCOVA and Linear mixed effects model
What is the best way to analyze these data:
Subjects are divided in two "Group" (Treatment A and B).
"Weight" is recorded before and 3 months after treatment.
Outcome variable: ...
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Can I do a PCA on repeated measures for data reduction?
I have 3 trials each on 87 animals in each of 2 contexts (some missing data; no missing data = 64 animals). Within a context, I have many specific measures (time to enter, number of times returning ...
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Unbalanced mixed effect ANOVA for repeated measures
I have data from patients treated with 2 different kinds of treatments during surgery.
I need to analyze its effect on heart rate.
The heart rate measurement is taken every 15 minutes.
Given that ...
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Are degrees of freedom in lmerTest::anova correct? They are very different from RM-ANOVA
I am analyzing the results of a reaction time experiment in R.
I ran a repeated measures ANOVA (1 within-subject factor with 2 levels and 1 between-subject factor with 2 levels). I ran a similar ...
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Which multiple comparison method to use for a lmer model: lsmeans or glht?
I'm analyzing a data set using a mixed effects model with one fixed effect (condition) and two random effects (participant due to the within subject design and pair). The model was generated with the <...
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Linear regression with repeated measures in R
I was unable to figure out how to perform linear regression in R in for a repeated measure design. In a previous question (still unanswered) it was suggested to me to not use ...
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Repeated measures analysis: why nest experimental factors within subject factor?
Consider a pure repeated measures design, with (let's say) 3 experimental within-subject factors A, B, and C, and (for simplicity) 2 levels per factor. So we have 2*2*2 = 8 measurements per subject.
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Precisely how does R's coxph() handle repeated measures?
Context
I'm attempting to understand how R's coxph() accepts and handles repeated entries for subjects (or patient/customer if you prefer). Some call this Long format, others call it 'repeated ...
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How to correctly treat multiple data points per each subject
I am currently arguing with someoe on how to correctly treat data with multiple measurements for each subject. In this case data was gathered for each subject within a short time for different ...
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Multiple Membership vs Crossed Random Effects
I see that there is a multiple-membership tag, but I can't find a good explanation of what a multiple membership model is, or how to go about fitting one.
In my limited understanding, it seem very ...
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How to write the error term in repeated measures ANOVA in R: Error(subject) vs Error(subject/time)
My question is very closely related to a previous post
Specifying the Error() term in repeated measures ANOVA in R. However, I would like to get more insight into how to define the error term.
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Develop a statistical test to distinguish two products
I have a data set from a customer survey, I want to deploy a statistical test to see whether there is significance difference between product 1 and product 2.
Here is a data set of customers' reviews....
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Understanding repeated measure ANOVA assumptions for correct interpretation of SPSS output
I am investigating whether different reward conditions may affect task performance. I have data from a small study with two groups, each with n=20. I collected data on a task that involved performance ...
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Non-normally distributed data - Box-Cox transformation?
I have data that is not normally distributed. The problem seems to be that there are too many of one value relative to other values.
What I have tried to make data normal:
I have tried a log ...
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If a statistic doesn't reveal a significance, do I have to calculate power for it?
Following the design and data described in this question, I did a simple one-way within-subjects repeated-measures (RM) ANOVA and found some significant p-values. I then applied non-orthogonal post-...
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Friedman's test and post-hoc analysis
I am carrying out a statistical analysis for my research. I am using a Friedman's test with post hoc analysis. At present I am using the function ...
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Which stats tests to use? Bee flight activity quantified during an eclipse
I'm trying to perform a statistical analysis but not sure what test is most appropriate. The experiment and snippet of sample data are below:
Methods: Bee flights from a beehive were recorded, ...
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Variance of Cohen's $d$ for within subjects designs
Based on this paper by Lakens 2013, I understand there are two recommended ways for calculating Cohen's $d$ for within subjects measures.
Cohen's $d_{rm}$ (which assumes the correlation between ...
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Comparing the within-subject variance between two groups of subjects
If each subject has repeated a test multiple times, I am able to compute the mean and variance of their performance. (I am assuming the results to be normally distributed).
1) If it is the variance ...
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Why is Pillai's trace equal to partial eta squared in a repeated measures MANOVA (profile analysis)?
I conducted a repeated measures MANOVA using the GLM command in SPSS, with one between-subjects IV (two levels) and 10 DVs (repeated measures). According to Tabachnick and Fidell (Book: Using ...
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Random intercepts model - one measurement per subject
I have repeated measurements on several hundred subjects. I plan to fit a random intercepts model. Most subjects have 3 to 4 measurements but about 20% only have one measurement.
For the subjects ...
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Equal standard errors for all levels of a categorical factor in lmer
I have a question about the standard error of mixed model parameters estimated using the lmerTest package.
I have 12 sites with 6 treatments over each site. I ...
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Accounting for time in repeated measures glmm, R
I have some count data of advanced stage juvenile snails in tanks that are sampled every 4 days for 4 sample points. I want to see how much the snail development stages change with a changing dosage ...
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Repeated ANOVA unbalanced data
I did experiment on one group of rats, the group was tested during 8 days, this is the first stage. The same group was also tested again but this time the test phase was 7 days. I tried to do my ...
Monica
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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 here:
...
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