Linked Questions

49
votes
2answers
40k views

What is a difference between random effects-, fixed effects- and marginal model?

I am trying to expand my knowledge of statistics. I come from a physical sciences background with a "recipe based" approach to statistical testing, where we say is it continuous, is it normally ...
10
votes
1answer
3k views

Interpretation of Fixed Effects from Mixed Effect Logistic Regression

I am confused by statements at a UCLA webpage about mixed effects logistic regression. They show a table of fixed effects coefficients from fitting such a model and the first paragraph belows seems to ...
11
votes
1answer
11k views

Marginal model versus random-effects model – how to choose between them? An advice for a layman

In searching for any info about marginal model and random-effects model, and how to choose between them, I have found some info but it was more-or-less mathematical abstract explanation (like for ...
10
votes
1answer
9k views

Difference between marginal and conditional models

A marginal model accounts for the correlation within each cluster. A conditional model also takes into account the correlation within each cluster. My questions are: Does a marginal model models ...
5
votes
2answers
3k views

Conditional vs. Marginal models

I have data with an outcome of 0 or 1 (binary) representing success or failure. I also have two comparison groups (Treatment vs. Control). Each subject in the study contributed 2 observations (the ...
2
votes
1answer
4k views

Subject specific vs population average predictions

I am in doubt whether in my thesis I should report on the subject specific predictions of the probability to respond with an 'I don't know' answer, or the population average. Consider for example the ...
2
votes
2answers
1k views

Random slope and intercept correlation. Not consistent in output vs manual calculation

Lets say individuals are nested within each ID and I am trying to a predict level 1 outcome Y from a level 1 predictor X with random slopes and intercepts. Using the nlme package in R, I ran the ...
7
votes
2answers
1k views

Why is the estimated variance of a random effect not equal to the variance of its BLUP estimates? [duplicate]

I am learning mixed effect model from here. I built a simplified model and trying to extract the $\gamma$ vector from linear mixed effect model $$y=X\beta+Z\gamma+\epsilon$$ then calculate ...
1
vote
1answer
665 views

Covariance matrix for the random effect in mixed effects model

According to this post, matrix Omega and sigma are in the results of lmer when we fitting ...
1
vote
0answers
34 views

Interpreting VarCorr estimates versus cor(ranef()) in lme4 mixed models

I am following-up this and this thread because I found it very difficult to understand the implications of using each of the two types of random-effect correlations. In particular, I fitted model like ...