Linked Questions

63 votes
2 answers
67k 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 ...
N26's user avatar
  • 1,955
10 votes
2 answers
3k 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 ...
Haitao Du's user avatar
  • 36.6k
10 votes
2 answers
10k 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 ...
user3275222's user avatar
4 votes
2 answers
4k 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 ...
Matata's user avatar
  • 641
3 votes
2 answers
3k 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 ...
Hotaka's user avatar
  • 1,174
16 votes
1 answer
17k 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 ...
benjamin jarcuska's user avatar
15 votes
1 answer
14k 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 ...
B_Miner's user avatar
  • 8,470
11 votes
1 answer
11k 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 ...
jamie's user avatar
  • 141
3 votes
1 answer
6k 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 ...
Marloes's user avatar
  • 790
1 vote
0 answers
483 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 ...
Carlotta Lega's user avatar