8
votes
Accepted
Different results between ANOVA and Linear Mixed Effects
The anova function returns the sequential tests on the model (the aov function would be used if you wanted to compare to ...
- 50.6k
7
votes
When to use fixed effects or multi level models in regression?
Like Shawn, I see no need for a mixed model (aka multilevel model). There's no reason your errors should not be independent in the "regular" regression and that is the problem that MLM or ...
- 109k
7
votes
Accepted
When to use fixed effects or multi level models in regression?
Theoretically, there is nothing stopping you from using a two-level random effect, but I think a mixed model here would be complete overkill. I would just fit a model that treats sex as a categorical ...
- 8,210
5
votes
Accepted
Residual error covariance structure in longitudinal mixed models
Indeed, when you include functions of time in the design matrix of the random effects you account for serial correlations in the repeated measurements data. The more complex functions of time you ...
- 19.9k
4
votes
Different results between ANOVA and Linear Mixed Effects
First, apart from Greg's excellent note about sequential vs. simultaneous tests, I wonder why you think the results should be more or less the same.
And for your final question:
How should these ...
- 109k
4
votes
What is the procedure to specify a random effects design matrix?
The random effects in mixed-effects models are used to account for correlations in grouped/cluster data. The two main settings of such data are multilevel and longitudinal designs or combinations of ...
- 19.9k
4
votes
How to structure repeated measures in GLM based on my study design? Nested or not nested
From the description of your study design, you appear to have a hierarchical/nested structure, where each of 5 Logs "belong" to one and only one ...
- 56.5k
3
votes
SAS fails to fit a mixed model
The SAS model you have fitted is not the same as the one you fitted with lme4::lmer. You have specified an unstructured variance-covariance matrix for the residual ...
- 56.5k
2
votes
Accepted
Modelling treatment strength in a mixed-effects model?
From the description, I don't see any problem with adding the variable treatment strength as a fixed effect. However, I think there are a few other issues here.
- ...
- 56.5k
2
votes
Controlling for Baseline Levels in Mixed Effects Modeling: Comparing Different Solutions
The details depend on the specifics of study design, so I can't say that there is a "consensus" applying to all circumstances. There are some principles, however, that apply to the specific ...
- 86.4k
2
votes
SAS Proc Mixed Repeated VS Random (or Both)?
The main difference between these models is that you are treating timepoint as categorical in the first model:
...
- 56.5k
1
vote
Extreme values affecting mean in regression analysis
Welcome to CV. Yes, both analyses could be affected by extreme scores. What to do about it depends on details, but here are some thoughts.
I am not usually a fan of transforming data, but here, I ...
- 109k
1
vote
Significant pairwise comparisons from emtrends but marginal means are not-significant?
As you know, the emtrends part of the output shows whether the continuous predictor's slopes for each categorical x categorical combination differ from zero and the contrast part shows whether they ...
- 1,086
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