Refers to a class of models developed to account for correlation that may occur within nested data.

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2
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1answer
21 views

Repeated measures anova or linear mixed model?

I have behavioural observation data on subjects (individuals) on which I did two kinds of tests. One test measured subjects' latency to feed and the second test measured their aggressive interactions. ...
1
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1answer
23 views

Simpson's Paradox & Random Effects

Simpson's effect is key to understanding potential pitfalls in medical research, particularly in the area of meta-analysis, where multiple studies with dissimilar methodologies are brought together to ...
2
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0answers
42 views

Estimating medians and modes of skewed distributions using GLMs

Edited question (less vague hopefully) I am wondering why for generalized linear models with Gamma, Poisson and Negative Binomial distributions that there appears to be no discussion about estimating ...
0
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0answers
8 views

Grand-mean center a log transformed variable in a mixed model

I have a linear mixed effects. I want to grand-mean center my variables so I can interpret my intercepts as adjusted group means. I have an income variable, natural log transformed. How do you ...
0
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0answers
12 views

How should I build my quadratic mixed-effects model for repeated measures for gauging the effect of time?

Multiple subjects were each exposed to an event. I measured a hormone 12 times (-60, -30, -10, -5, 0, 5, 10, 20, 30, 40, 50, 60) Time (minutes) is centered around the onset of the event. We know the ...
0
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0answers
47 views

Hessian Hell: Why won't this converge

I want to track and compare within-subject trajectories of performance over time in study (TIME) on three within-subject task conditions (task_index) categorical variable. I am using ID as my subject ...
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0answers
17 views

Restricted Maximum Likelihood Estimation for Linear Mixed Model

The maximum likelihood estimation procedure for linear mixed model is described in this link. It seems to me that something is wrong there. In their Restricted Maximum Likelihood section the first ...
0
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0answers
14 views

Mixed Effects Models - Correlation in the Random Effects

Is it a problem if I have correlation between my random effects variables? Correlation in my fixed effects can bias my model and need to be addressed through an interaction term or some other ...
0
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1answer
11 views

Correlation between standardized residuals and fitted values in a linear mixed effect model: Course of action?

I am fitting a linear mixed effect model in R with lme from nlmer, using the approach described in Zuur et al. "Mixed Effects ...
0
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0answers
16 views

comparison of N groups of independent individuals curves: summary-variables or nonlinear mixed effect model?

I want to assess wether there is a significant difference among two groups, based on a sample of independent individual curves in each group. The logical next step is to try to understand what ...
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0answers
10 views

Two time series within one another

I took 5 observations per individual over the course of 10 minutes (continuous measure). Individuals came from different treatment groups. There is a substantial increase in my DV over the 4 hours ...
1
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1answer
33 views

linear mixed model on continuous, zero-trunctated data

I have a dataset with one continuous response variable (time), a 'treatment' explanatory variable and 5 other fixed factors: ...
0
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0answers
19 views

Multilevel model analysis of dyad data

I'm trying to understand why when conducting a multilevel model analysis the Hessian matrix is not positive definite (using SPSS). The data I'm analyzing are responses from individuals who are grouped ...
0
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0answers
14 views

controlling for a fixed factor

n the model below, I am looking at the effects of language (2 levels) and cognitive control (scaled continuous factor) on picture naming latencies (DV). However, I need to do this while controlling ...
0
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0answers
22 views

Mixed-effect or multi-level model (or other) for multivariate repeated-measures data? [R]

I have a dataset consisting of: 2 groups of plants (Group 1, Group 2) living in 10 different neighboring fields (...
2
votes
1answer
47 views

Calculating Overall Relative Bias

I am in some trouble to understand how is to calculate the overall relative bias. In this link, there are results of overall relative bias in "Parameter estimates" sub-section under "Results" ...
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0answers
31 views

Multilevel Model in Matrix Form

A two-level model, with one explanatory variable at the individual level $(X)$ and one explanatory variable at the group level $(Z)$ : ...
0
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0answers
26 views

How to account for order/ repeated measures in a linear mixed model?

My data involves: 7 subjects who all received three different treatments (A, B and C), separated by one week Each subject received treatment A first, although treatments B and C were completed in a ...
1
vote
1answer
43 views

Underestimated Coverage probability

Let $U0$ denotes intercept variance and $U1$ denotes slope variance. Given that the coverage rate for the intercept variance is $91$% $(U0)$ , and the coverage rate for the slope variance is $91.2$% ...
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0answers
76 views

How compute the Intra-Class Correlation for a Negative Binomial Mixed Model in lme4

I have a negative binomial mixed model with counties nested within states. I've read that the formula for the ICC for a negative binomial model is: found here: ...
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0answers
21 views

Notation in two-level regression model

In this pdf, formula of two-level regression model is written as : $$Y_{ij}=\beta_{0j}+\beta_{1j}X_{ij}+e_{ij}$$ and in the pdf $e_{ij}$ is referred as individual level Residual . But I am not ...
4
votes
1answer
118 views

Statistical Significance Issue in Mixed Model

A multilevel model, with one explanatory variable at the individual level (X) and one explanatory variable at the group level (Z): ...
0
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0answers
17 views

How can I test which timepoints are different between treated groups and control group?

Which test should I use to find out which tested days are sigificantly different between treated (red and blue) and control group (dashed) ? I don't want full cross-testing between all categories, ...
4
votes
0answers
68 views

Testing Fixed and Random Effect of Mixed Model

This pdf illustrates nicely how is to test the random effect of multilevel model . But I am simulating data from a two-level model and estimating the parameters of the model for various combination of ...
1
vote
1answer
29 views

How to handle age and timepoint variables in a mixed-model for longitudinal data?

I have a longitudinal dataset: DV: Task performance on three within-subject conditions at each time point IVs Timepoint (variable interval, up to three occasions, missing data at random) Age at ...
3
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0answers
30 views

Convergence Criteria in R's lmer

In this article , it is written in the Convergence and estimation bias para that : It is important to consider the minimum number of cases needed to ensure the model converges and that sample ...
0
votes
1answer
29 views

Missing data and covariate analysis

I'm working on a model which has been fitted to longitudinal data (using mixed effects regression). I'm also investigating the effects of about 6 covariates on this model. Covariate A (continuous ...
1
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0answers
32 views

Nesting in mixed effect models

I am interested in how a response varies between time periods, and regions. My question revolves around nesting of random effects, specifically putting site (unique within each region) as a random ...
5
votes
1answer
117 views

What are the fitted values in a random effects model?

Consider a linear random intercept model: \begin{align} y_{ij} &= A_{i} + \varepsilon_{ij} \\ A_{i} &\sim N(0,\tau^2) \\ \varepsilon_{ij} &\sim N(0,\sigma^2) \end{align} where, $A_i$ ...
0
votes
1answer
36 views

r glmer warnings: model fails to converge & model is nearly unidentifiable

I have seen questions about this on this forum, and I have also asked it myself in a previous post but I still haven't been able to solve my problem. Therefore I am trying again, formulating the ...
0
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0answers
27 views

How to turn nlme syntax into manuscript appropriate equation?

I ran an linear mixed-effects analysis in R using the nlme package. I would like to write out the algebraic equation of the model's specifications. Unfortunately, I do not know exactly how to ...
0
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0answers
16 views

How is the confidence interval of variance component calculated?

How is the confidence interval of variance component calculated ? As far I know , confidence interval of variance is calculated as : ...
0
votes
1answer
34 views

Why are the Wald standard errors often very poor estimates of the uncertainty of variances?

As from this post as @Ben Bolker pointed out that : .. note that these (as often pointed out by Doug Bates) the Wald standard errors are often very poor estimates of the uncertainty of variances, ...
0
votes
1answer
58 views

Difference between two lmer model

Can you please explain where is the difference between the following two models : ...
0
votes
1answer
24 views

Why CLMM function for ordinal mixed logistic regression changes the means?

I am using CLMM to run the ordinal mixed logistic regression model as the DV is ordinal number from 1 to 9 (rating scale). First I read the file and change the DV into ordinal using these commands: ...
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vote
0answers
43 views

Interpretation of various output of “lmer” function in R

library(lme4) fm1 <- lmer(Reaction ~ Days + (Days | Subject), sleepstudy) The notation (Days | Subject) says to allow the ...
0
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0answers
12 views

Correlated errors within group with nonvarying dependent variable

I am trying to run a model in R to show how well one survey (SurveyA) predicts responses to another survey (SurveyB). SurveyA has 20 questions and we get an estimate of the participant's parameter ...
0
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0answers
20 views

Obtaining significance for mixed GLMMs on count and binary data

I'm new to the software R and am trying to compute statistics on data from experiments on the offspring of lizards from two different thermal treatments - looking specifically at differences in their ...
0
votes
1answer
16 views

Interpretation of “Same Slope” in Multilevel Modeling Example

An example of multilevel modeling : Consider an educational study with data from students in many schools,predicting in each school the students’ grades y on a standardized test given their scores on ...
0
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0answers
18 views

linear mixed model with paired and unpaired effects

Here is my problem: 20 subjects performed different movements: arm flexion, abduction and rotations [Ma, Mb, Mc]. In addition each of these movements were performed with or without a load of 3 kg ...
2
votes
1answer
83 views

Notation of Variance of Residuals in Multilevel Modeling

I am having some trouble to understand the notation of variance of residuals in multilevel modeling . In this paper "Sufficient Sample Sizes for Multilevel Modeling" , in p.87 below equation (3) , ...
0
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0answers
17 views

Repeated measures mixed model with nested data

I have been trying to figure out how to run the stats I need for this study for weeks and despite reading endless amounts of information am not much the wiser! If anyone can help, I would be hugely ...
4
votes
2answers
78 views

How to simulate a random slope model

I would like do create a mixed linear model for an unbalanced dataset (different number of events per subject and a few missing values for some time points). I am using ...
0
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0answers
12 views

Hypothesis testing in GLMMs - How to set up sequential LRTs

I'm fitting a generalized linear mixed effects model to my data. I have three fixed effects, and one random effect nested within one of the three fixed effects. The response variable is a count, ...
0
votes
1answer
35 views

How to compute MSE of linear mixed model

Considering the linear mixed model, $y=X\beta+Zb+e$. After parameter estimation, we want to compute the MSE of the model. First, we compute the BLUP of b. Then $MSE = ||y-X\beta^*-Zb^*||^2$. Is the ...
2
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0answers
32 views

Modelling against “day” or “day^2” in to look at change over time?

I'm a masters student trying to model changes in behaviour, heart rate variation and faecal cortisol as welfare measures in sheep over the course of 22 days. Days -4 to -1 is used as baseline, day 0 ...
0
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0answers
13 views

3 categorical variables (2 are repeated measure variables) and 1 continuous variable - what analysis?

I originally ran a 2(inclusionary condition)x2(interaction with close other vs stranger)x2(time of pain measurement-repeated variable) mixed manova with 2 dependent variables(physical pain ...
0
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1answer
32 views

linear regression vs linear mixed effect model coefficients

It is my understanding that linear regression models and linear mixed effect regression models will produce the same regression coefficients (i.e., fixed effects); however, linear regression models ...
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0answers
44 views

How can I test variance explained by the factor group if each subject in the group comprises a different number of measurements?

The data structure I have 2 groups with 30 subjects each. Each subject has a different number of fibers (approximately 46000 +/- 3000) of different length (see histogram). My goal is to determine how ...