Tagged Questions
0
votes
1answer
35 views
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 ...
1
vote
0answers
46 views
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 ...
4
votes
0answers
63 views
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 ...
0
votes
1answer
136 views
How do I cross error terms in Stata's xtmixed (examples inside) like lmer's +(a*b*c|s)?
Let's say I have an experiment with three within-subject factors, A, B, & C. Data looks like this.
...
2
votes
1answer
207 views
2
votes
1answer
183 views
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 ...
0
votes
0answers
112 views
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 ...
1
vote
1answer
144 views
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 ...
0
votes
0answers
145 views
Homogeneity of variance in ANOVA mixed model?
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.
I have checked with SPSS: variance is ...
0
votes
1answer
474 views
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 ...
5
votes
2answers
1k 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 ...
0
votes
0answers
59 views
How to handle messed up block design?
Let's pretend we have got a randomized block design with three blocks. The aim is to study the effect of fertilisation and irrigation on productivity in an apple plantation. Within each block there ...
2
votes
1answer
233 views
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 ...
1
vote
1answer
123 views
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 ...
1
vote
0answers
244 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: ...
1
vote
0answers
103 views
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 ...
2
votes
1answer
801 views
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 (...
1
vote
2answers
2k views
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 ...
3
votes
0answers
160 views
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 ...
2
votes
0answers
133 views
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 ...
3
votes
1answer
344 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 ...
2
votes
1answer
102 views
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 ...
3
votes
0answers
237 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 ...
2
votes
2answers
192 views
Confidence intervals in a mixed model
Consider the following mixed model: $$(y_{ijk} \mid \mu_{ij}) \sim_{\text{i.i.d}} {\cal N}(\mu_{ij}, \sigma^2), \quad k=1, \ldots K $$ $$ \begin{pmatrix} \mu_{i1} \\ \vdots \\ \mu_{iJ} \end{pmatrix} ...
5
votes
2answers
2k views
When is a repeated measures ANOVA preferred over a mixed-effects model?
In response to this question, regarding whether my design where I randomly presented participants with pictures from different categories was an example where I should use a repeated measures ANOVA, I ...
1
vote
1answer
421 views
How to interpret 3-way interaction with one continuous variable in mixed model
I have problems interpreting the direction of the effects in my model. Can you help me with this?
I conducted an experiment which includes
between subject factor:
group=2 (coded as 0-1)
within ...
2
votes
1answer
383 views
Two-way mixed effects ANOVA model
Consider the two-way ANOVA model with mixed effects :
$$
Y_{i,j,k} = \underset{M_{i,j}}{\underbrace{\mu + \alpha_i + B_j + C_{i,j}}} + \epsilon_{i,j,k},
$$
with $\textbf{(1)}$ : $\sum \alpha_i = ...
1
vote
0answers
142 views
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 ...
1
vote
0answers
39 views
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 ...
17
votes
1answer
4k 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 ...
5
votes
1answer
2k views
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 ...
2
votes
1answer
349 views
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 ...
7
votes
2answers
3k views
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.
...
1
vote
2answers
2k 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: ...
5
votes
2answers
562 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 ...
4
votes
1answer
183 views
How can I treat blocks in a split plot design?
In a field experiment involving crops, what is the difference in considering block as random or otherwise as fixed factor?
As far as I understood, random means that conclusion can be extended to other ...
9
votes
2answers
4k views
Multiple comparisons on a mixed effects model
I am trying to analyse some data using a mixed effect model. The data I collected represents the weight of some young animals of different genotype over time.
I am using the approach proposed here:
...
7
votes
3answers
1k views
Effect size for interaction effect in pre-post treatment-control design
If you choose to analyse a pre-post treatment-control design with a continuous dependent variable using a mixed ANOVA, there are various ways of quantifying the effect of being in the treatment group.
...
12
votes
4answers
1k views
Follow up: In a mixed within-between ANOVA plot estimated SEs or actual SEs?
I am currently finishing a paper and stumbled upon this question from yesterday which led me to pose the same question to myself. Is it better to provide my graph with the actual standard error from ...
