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Mixed (aka multilevel or hierarchical) models are linear models that include both fixed effects and random effects. They are used to model longitudinal or nested data.

3 votes
1 answer
236 views

Why does this mixed model produce discrepant output in SPSS and R?

I've been working with an example from the Heck et al (2013) textbook, which gives the following model: $Y_{ij} = \gamma_{00} + \gamma_{01}\text{ses_mean}_j + \gamma_{02}\text{pro4yrc}_j + \gamma_{03} …
user1205901 - Слава Україні's user avatar
3 votes
2 answers
155 views

What's an example of a situation in which it makes sense to assume random slopes but a fixed...

I'm referring to multilevel modelling. Field (2013) writes: It’s worth noting that it would be unusual in reality to assume random slopes without also assuming random intercepts, because variab …
user1205901 - Слава Україні's user avatar
2 votes
0 answers
38 views

Mixed models: Why are deviations of each level of the grouping factor's value from the popul...

Bolker (2015) talks of a research scenario in which site is the grouping factor. He writes on p.312 that Treating site as a random effect compromises between the extremes of pooling and estimating …
user1205901 - Слава Україні's user avatar
2 votes
1 answer
629 views

In multilevel modelling, what's the interpretation of $\gamma_{00}$?

I am thinking of a null model (also known as a random-effects ANOVA, or intercept-only model) $$ y_{ij} = \gamma_{00} + u_j + e_{ij} $$ where $u_j$ are the level-2 residuals and $e_{ij}$ are the lev …
user1205901 - Слава Україні's user avatar
2 votes
0 answers
522 views

Mixed models: When can adding a predictor increase the residual variance?

I saw that Andrew Gelman had discussed this issue in one of his books, and a relevant excerpt is presented here. He also very briefly discusses this issue in his blog post here. In the book excerpt G …
user1205901 - Слава Україні's user avatar
1 vote
0 answers
27 views

Principles for deciding to model a variable as both random and fixed in the same analysis

There are quite a lot of questions which touch on this issue, but there does not seem to be any that sets out any general principles for deciding when it would be a good idea (or a bad idea, or a poin …
user1205901 - Слава Україні's user avatar
2 votes
1 answer
1k views

Multilevel modeling: Why aren’t level-1 predictors allowed in level-2 equations?

I’m reading a presentation by Preacher, who gives the following level-1 and level-2 equations Level 1 $y_{ij} = \beta_{0j} + \beta_{1j}x_{1ij} + \epsilon_{ij}$ Level 2 $\beta_{0j} = \gamma_{00} + \ga …
user1205901 - Слава Україні's user avatar
2 votes
1 answer
360 views

Why did removing the between-subjects factor from a two-way mixed ANOVA change the SSwithin?

I have been playing with this SPSS data file, which is a class example from a university I am not enrolled in. In the original file there are 10 men and 10 women. I did a two-way mixed ANOVA with gen …
user1205901 - Слава Україні's user avatar
1 vote
1 answer
82 views

Longitudinal multilevel models: deleting the baseline timepoint

I'm reading a paper which reports a multilevel model with random intercepts and slopes in which individual people's score on a scale of anxiety is assessed at five different timepoints. So the timepoi …
user1205901 - Слава Україні's user avatar
3 votes
1 answer
759 views

Why does this 3-level multilevel logistic regression fail to converge?

I'm running a multilevel logistic regression in which I estimate the probability the authors of scientific papers will make a particular sort of error in reporting a null hypothesis significance test …
user1205901 - Слава Україні's user avatar
0 votes
0 answers
66 views

When will a cross-level interaction increase the slope variance?

Heck et al (2012) give the following model $Y_{ij} = \gamma_{00} + \gamma_{01}\text{ses_mean}_j + \gamma_{02}\text{pro4yrc}_j + \gamma_{03}\text{public}_j + \gamma_{10}\text{ses}_{ij} + u_{0j} + u_{1j …
user1205901 - Слава Україні's user avatar
1 vote
1 answer
1k views

What kind of linear mixed model is most appropriate for this data?

I previously wrote about this data here, and was advised that a linear mixed model applied to the raw data would provide "more precision and power" than the originally suggested approach of a regressi …
user1205901 - Слава Україні's user avatar
3 votes
0 answers
2k views

Is this a complete list of the assumptions of linear mixed-effects models?

Crawley (2012) p682 writes: There are five fundamental assumptions of linear mixed-effects models: Within-group errors are independent with mean zero and variance $σ^2$. Within-group er …
user1205901 - Слава Україні's user avatar
15 votes
2 answers
915 views

ICC as expected correlation between two randomly drawn units that are in the same group

In multilevel modelling the intraclass correlation often gets calculated from a random-effects ANOVA $$ y_{ij} = \gamma_{00} + u_j + e_{ij} $$ where $u_j$ are the level-2 residuals and $e_{ij}$ are th …
user1205901 - Слава Україні's user avatar
7 votes
1 answer
4k views

How is repeated-measures ANOVA a special case of linear mixed models?

In this comment @gung mentions that On a different note, I think it's fair to think of RM ANOVA as a special case of linear mixed models. and a subsequent comment concurs with this. I under …
user1205901 - Слава Україні's user avatar

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