# Tagged Questions

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### How to deal with unbalanced group sizes in mixed design analysis?

I have 2 x 2 x 2 mixed design with two between subject factors (sex, organizer) and one within subjects factor (task). The group sizes of the 'sex'-factor is unequal. When I perform a factorial ...
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### Compare variance and point statistics in a 3 way group

I need some help on this analysis. I have 3 groups of individuals, different the level and kind of physical activity. For each individual I have the heart rate, taken every minute for ~24h. (each ...
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### Mixed Model t Test (Toothaker’s t-Test)

I'm trying to do a follow up test for a mixed model ANOVA, and I figured that I need do a Mixed Model t test also known as Toothaker's test. I just don't know how do it. I was wondering if anyone has ...
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### Mixed Model ANOVA interpretation

I am using SPSS to analyse the 3-way mixed model ANOVA of my study. I have split my variables down to interpret simple interaction effects and found that whilst the graph displays an interaction ...
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### Interpreting 5-way Mixed Model ANOVA

I'm running a 2x2x2x2x2 mixed model ANOVA (on SPSS v21) for my study and found two 4-way interactions, one 5-way interactions and a couple of 3-way interactions. Whilst I understand how to interpret a ...
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### Is mixed measures ANOVA the correct test for my data?

I'm fairly new to statistics and I'm still trying to figure out the best way to analyse the data I have. The experiment has 2 groups of participants who perform 2 repetitions of a task that consists ...
116 views

### What does the anova() command do with a lmer model object?

Hopefully this is a question that someone here can answer for me on the nature of decomposing sums of squares from a mixed-effects model fit with lmer (from the ...
51 views

### Linear mixed model for repeated measures analysis with missing values

we have ran an experiment where we compared three interaction techniques for a 3d docking task. So we had two factors: the aforementioned technique type and a factor representing the direction ...
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### Help needed with interpreting mixed-model and factorial ANOVA

I really need help with an analysis I am doing. The study involves a comparison of two different treatments for bulimia (weight concern treatment and perfectionism treatment) and a combination of the ...
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### Biased distribution of covariate levels among batches

I am investigating the physiologic response (gene expression) of two groups of individuals (Group A and Group B) on a continuous environmental covariate in two different environments (E1 and E2). As I ...
139 views

### 5-way interaction

I am running a mixed factors ANOVA for a brain imaging study on language processing. The design includes four within-subject factors: complexity: simple/complex; agreement: correct/number ...
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### Mixed effects model or mixed design ANOVA in R

I'm wondering if you could quickly advise on the best statistical analysis for my data. I have a designed experiment with 12 plots within one larger area. This area was blocked into 6 to overcome ...
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### What is the difference between multilevel modeling and three factor nested mixed ANOVA

I have time nested in students, nested in teachers. How would this look in a three factor set up A x B x C? time = 3 occasions students = randomly assigned to four conditions teachers = 20 any ...
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### Interpret significant interaction but no main effect in repeated measures ANOVA

I have a model in which two groups are measured on one DV at pre- post- and 3 months following an intervention (the control group did not receive the intervention). I have an interaction effect, which ...
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### When to average samples in order to avoid pseudoreplication?

My question is when to average samples or when it is allowed to apply a mixed effects model. I have the following constellation: there is a cell-line experiment conducted in a 96-wellplate, meaning ...
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### Simple Mixed Model with 1 Fixed and 1 Random Effect

I have various datasets I need to analyse regarding soil properties, all in the same fashion, with one fixed effect (which is a position along a transect, indicating different land uses). Now my main ...
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### Which ANOVA is most appropriate?

So, I have a question for a proposal and I'm fairly certain I'm getting an incorrect answer from our local "stats guy". For the record, it's archival data so I can't change the items (which aren't ...
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### Comparing models of different types of ANOVA - multiple comparisons?

Statistical semi-novice question: Just following up this question, the fact that the three types of ANOVA exist with an unbalanced design, and that (presumably) you don't necessarily know a priori ...
203 views

### How do I cross error terms in Stata's xtmixed?

Let's say I have an experiment with three within-subject factors, A, B, & C. The data looks like this. ...
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### lmer interpretation of correlation

I have the following output: ...
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### Checking normality of residuals in 2x2 mixed methods ANOVA

I am running a 2x2 mixed method ANOVA (with one between-group factor and one within-group factor - time 1 and time 2). I want to check whether the assumption of normality of residuals is met. When I ...
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### Determining sample size needed in a 4-way mixed ANOVA to reach significance

I have a data set for a 2 (between) x 3 (within) x 3 (within) x 3 (within) mixed ANOVA. I need to find the sample size necessary to find a significant result for one of the 3-way interactions ...
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### Variances not homogeneous problem in ANOVA mixed between-within subjects, too bad?

I'm conducting a 2x3 mixed between-within subjects ANOVA (group x time). I have 20 participants, 10 for each group, who undergo all the 3 measures over time. Levene's test of equality of variances is ...
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### Normality test for anova mixed model in SPSS: I did it in two ways but the results are contrasting

I'm conducting an ANOVA mixed model 2 X 3 (group X condition). Right now, I'm checking for the assumptions of ANOVA, such as normality. I should check indipendently for group and condition, right? I ...
2k views

### Post hoc test in a 2x3 mixed design ANOVA using SPSS?

I have two groups of 10 participants who were assessed three times during an experiment. To test for differences between groups and across the three assessments, I ran a 2x3 mixed design ANOVA with ...
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### Prediction interval for the one-way random effect ANOVA

I don't find a textbook presenting prediction intervals for mixed models. Moreover I'm only looking for a prediction interval for the balanced one-way random effect ANOVA model. Do you know a formula ...
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### What is the ANOVA model to use for a 2x2 factorial experiment with units measured 3 times each?

If I were to set up an experiment examining the effects of exercise, and coffee consumption on the number of hours slept, what would the be the ANOVA model that I should use, given: 16 volunteers ...
373 views

### Mixed linear model with repeated measures in SPSS

I'm trying to run a mixed linear model analysis with SPSS. When I try to run the analysis, SPSS gives the following error message: ...
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### Mixed repeated measures Anova

I'm trying to assess the influence of fertilisation and irrigation on biodiversity in a complete randomized block design. I have two treatments, one control and two blocks. Treatments went on for ...
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### How to interpret an interaction effect in SPSS output for a repeated measures anova with between and within group factors?

I have conducted a repeated measures ANOVA, with 2 factors: One between factor (Ex_control: exercise intervention versus control) One within factor (...
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### Testing normality assumptions for linear mixed models and mixed (repeated) GLM ANOVA in SPSS

I have a mixed design that includes both repeated (condition) and between (sex and genotype) subjects factors. I would like to assess whether my data meets the normality assumptions for 1) General ...
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### How can I compute a repeated measurement ANOVA with a mixed model?

It is my task to program a mixed model. The data is from 20 experimental subjects, who were measured under 2 factors. Factor A has 7 levels, factor B has 3 levels. So, that for every subject I got 21 ...
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### Can I used a repeated measures ANOVA or do I have to use a multivariate ANOVA?

I don't feel very comfortable with stats (still using simple programmes like SPSS rather than R!), and have a question about which is the best test to use with the following design: I have performed ...
484 views

### How to choose an appropriate covariance structure for a simple one-way within-subjects RM ANOVA design?

It is postulated that one of the main issue is to find an appropriate covariance structure for repeated measures designs [Ref1]. SAS' PROC MIXED contains a number of covariance structures. Despite ...
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### Effect of %in% in a model formula?

What is the meaning and effect of %in% in a model formula? It is apparently used for nesting of one variable into another in a variety of analysis (manova, anova, regressions) in a few published ...
312 views

### Formulating a mixed model with nested fixed and random effects

I'm analysing the results of an experiment using a mixed (fixed and random-effects) ANOVA with nested effects and I just need someone to confirm that I have the right model. The effects in the design ...
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### What is best for comparing variability for environmental time series data: repeated-measures ANOVA or linear mixed models?

I've collected environmental data on the dust level using direct-reading instruments. The outputs from the instruments are concentrations recorded at each minute over 1 hour. The data collected at ...
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### Investigate change in mean levels of risk within a service- alternative to unbalanced repeated measures ANOVA

Not sure if this is as complicated as it's ended up in my head, here goes. I have a series of measurements which measure how risk-prone psychiatric patients are (hereafter referred to as HCR and it's ...
5k 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 ...
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### Why are degrees of freedom so high in repeated measures mixed models?

I have been running a repeated measures mixed model in SAS and the denominator degrees of freedom for the F statistic seems to be really high. In this case I have roughly 200 individuals and three ...
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### How to get equivalent ANOVA in R for a model with and without a random effect?

My question is: Is there a way to either force Anova() to somehow analyze gls objects (which internally are almost identical ...
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### Paired, repeated-measures ANOVA or a mixed model?

I have been asked to analyse some data from a clinical trial looking a two methods of measuring blood pressure. I have data from 50 subjects, each with between 2 and 57 measures using each method. ...
3k views

### Problem with ANOVA repeated measures: “Error() model is singular”

I need an help because I don´t know if the command for the ANOVA analysis I am performing in R is correct. Indeed using the function aov I get the following error: ...
636 views

### How to fix the threshold for statistical validity of p-values produced by ANOVAs?

I have run experiments on a group of users under two conditions, measuring the time it took users to finish their experiments. I used a cross-over design where half of the users started in the first ...