Questions tagged [mixed-model]

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.

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Putting the following linear mixed effect in matrix notation

I am used to seeing the linear mixed-effects model in the form: $$Y_{ij} = \mu + \alpha_i + \gamma_j + (\alpha\gamma)_{ij} + \epsilon_{ijk}$$ assuming $ \gamma_j i.i.d \sim N(0,\sigma^2_{\gamma})$ ...
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Additional steps for smoothing log transformation to establish RMSE? [closed]

A GMLE is too complex for the data, so I use a LME and have a log(DV + 1) ~ IV. If I want to calculate the RMSE, would it be principled to subtract 1 from all modeled values, then exponentiate these, ...
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Linear mixed model with many NAs

I am running a linear mixed effects model in R using the lmer4 package. I was wondering if my data is structured in the right way for this purpose. In a few words I have a response variable "...
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Single Observation with Some Groups. Multilevel model or other analysis?

I am having trouble determining which method to use to analyze my data. Here is the info: -575 observations nested within 292 groups -some groups only have one observation, the max number is 23 in a ...
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1answer
33 views

How to do logistic mixed regression with these data?

In this study, measurement was done on each subject at 3 time points (0, 4 and 80 hours). Each subject was then checked for some event. The data is in following form: ...
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31 views

Parsimonious Mixed Models

I recently read a paper on the trimming of random effect structure by Bates, Kliegle, Vasishth and Baayen (2015). My understanding is that the Parsimonious Mixed Model they proposed mainly follows the ...
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1answer
17 views

Mixed model for trial-based analysis

I conducted an experiment that investigated preferences for two-digit numbers. Each digit was randomly drawn from a list of digits between 1 and 9, with one digit presented at a leftish position and ...
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13 views

Converting Cohen's $F^2$ to Cohen's $D$

How can I convert Cohen's $F^2$ to Cohen's $D$? I am interested in calculating the effect size for the difference between two groups in a mixed model. The data is from a within-subjects experiment ...
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Using RMSE and AIC to compare three separate “final” models (one with double observations)?

I'm looking at three models (linear mixed effect) looking at crime. The first looks at total crime so there are ~96000 observations. In the second model, I look at crime as a function of crime type (...
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428 views

Obtaining p-values in a robustlmm mixed model via Satterthwaite-approximated DFs of the equivalent lme4 model?

I've used lme4 to fit a mixed model and could obtain p-values by using the lmerTest or afex packages. However due to heteroskedasticity (Levene Test) I also fit a robust model (rlmer command in the ...
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How do I interpret this hurdle model summary (pscl)?

A little bit about my data: I have four treatment groups: control, early, late, both. For each group, I counted nymphs and eggs on leaves on five different dates. The design is randomized complete ...
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How do I interpret results of a mixed effect linear regression with 7 independent variables accounting for variability of one dependent variable?

I have 7 moderators while fitting the mixed effect model using the metafor package, my results show many interactions and I am a bit confused on how to present ...
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Mixed Effects Logistic Regression w/ Repeated Measures for Observational Data

I am working on a study of how different scholarship programs at a university may influence student retention (i.e., if students are still enrolled at the university one year later). Each student can ...
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1answer
114 views

Problem with non-normal residuals (lmer function)

I work with animal personality and I am trying to analyze individual differences in response to certain stimuli. Taking this particular dataset as an example, I am analyzing how much distance animals ...
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Is this use of emmeans an appropriate way to calculate a 95% confidence interval for a parameter?

I generated data using the model $y_{i j} = \alpha_i + \beta_i x_{i j} + \epsilon_{i j}, i = 1, \ldots, 48, j = 1, \ldots, 16$, $\alpha_i \sim \text{N}(0, \sigma_{\alpha}^2)$, $\beta_i \sim \text{N}(\...
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Conditional intraclass correlation (ICC) from a linear mixed model as evidence for test-retest reliability?

In my experiment with two conditions (between-subjects design), participants completed a single-item scale three times: (1) before the experimental manipulation, (2) after the experimental ...
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1answer
24 views

Regarding modelling longitudinal variables using Two stage mixed effects modeling

I have a question about the basic understating of key statistical methodology. I came across the idea about two stage modelling to incorporate longitudinal predictors. Lets say there is a continuous ...
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1answer
22 views

Analysing change scores via linear mixed effects model with baseline adjustment?

I am still trying to find a model for a large dataset, approximately 1-5 measurements per patient (over time), one is the baseline value at t=0. The researcher is interested in the change over time ...
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1answer
57 views

Between-subjects, factorial, crossed, cross-classified: all the same thing?

Suppose I have a test with $j$ items taken by $i$ persons. I wish to obtain the mean item score (y) taking into account that both items and persons are a sample of ...
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1answer
223 views

Calculating sums of squares for mixed-model ANOVA

I'm trying to get an understanding of how to calculate the sums of squares values in a mixed-model ANOVA (mathematically, not just the syntax for R or SPSS!). I've been trying to figure this out for a ...
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1answer
22 views

Is there any harm in including all predictors of interest in an lmer() model?

I have a study in which ~60 participants rating a subset of 200 items. I have four potential predictors that I would like to use to predict those ratings. I will run an lmer() model including random ...
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1answer
291 views

Between-subject post hoc for $2 \times 3$ mixed ANOVA in SPSS

I think I got this, I just want to double check whether I'm interpreting the SPSS output correctly. So I am running a $2 \times 3$ mixed ANOVA with $3$ between-subject groups and a within-subject ...
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1answer
169 views

Explaining tourist numbers over time to historic sites, based on a set of predictors

I've been struggling for some time trying to figure out the most appropriate way to analyse some data. My task is to (hopefully) explain what may be driving the flow of visitors/tourists to two ...
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24 views

What is the best method to determine significance in a zero-inflated poisson model?

I am currently trying to run a zero inflated mixed effects model in R using the package glmmTMB following a significant test of zero-inflation (using the function testZeroInflation() in the package ...
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1answer
25 views

LRT comparing a random effects model and nested logistic regression model

I have a logistic regression model of the structure y ~ x1 + x2, and a generalized linear mixed model (GLMM) with random intercept and random slope, of the ...
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1answer
20 views

LMM: fixed effect significant in complex model, but not in reduced model

I constructed two models with lme4::lmer: decomposition ~ trait1 + trait2 + trait3 + (1|pair) all trait effects are highly ...
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Mixed effects/nested model giving different EMS tables in R and Minitab, and I believe Minitab is incorrect. Anyone know why it would be wrong?

I have a dataset at https://docs.google.com/spreadsheets/d/1PB_S7oX2Tqgz_BEUUcHfLOww0cNJ-IgN6B34UTequlw/edit?usp=sharing that shows a mixed model where Machine and Station are fixed effects and Power ...
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1answer
19 views

How to interpret differences in explained variance (both r2m and r2c) among models that are not nested?

I want to evaluate how well a device (dev.B) can predict accurately the values of another device (dev.A) that is used as a ...
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1answer
25 views

Mixed Effects Nesting

I have a simple model with mixed effects. I asked subjects ten questions, five easy and five hard, and saw how much they relied on advice, based on who their advisor was (algorithm or peer) and how ...
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3answers
790 views

Convergence of Latent Class Linear Mixed Model with LCMM in R

I am seeking help getting my latent class linear mixed models to converge using the LCMM package in R. I am studying common patterns of heroin and cocaine use over the life course of adults who have ...
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1answer
248 views

multiple imputation of longitudinal, time-unstructured data

I have a longitudinal dataset of radiation exposures of an occupational cohort. A percentage of the exposure values are missing and I would like to multiply impute the missing values (it is one option ...
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1answer
15 views

coefTest for Mixed Logistic in Matlab [closed]

I conducted a mixed logistic regression model in Matlab with fitglme and want to conduct post-hoc tests on specific data points of a continuous*categorical interaction. I have tried doing this using ...
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19 views

How to fit the correct multilevel (logistic) regression?

I want to study the link between hospital competition and mortality. The competition a hospital faces is measured by the Herfindalh-Hirschman index (HHI). So I want to know if a hospital's HHI is ...
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105 views

Why is the coverage of this lme4 confidence interval less than 95%?

I have data that can be described using the model $y_{i j} = \alpha_i + \epsilon_{i j}$, where $\alpha_i \sim \text{N}(\mu_{\alpha}, \sigma_{\alpha}^2)$ and $\epsilon_{i j} \sim \text{N}(0, \sigma_{\...
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2answers
4k views

generalized linear mixed models vs linear mixed effect models

What is the difference between generalized linear mixed models, and linear mixed effect models (lmer function in package lme4) in terms of distributions of the response variable? Do they both work ...
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2answers
190 views

How to export a formula from a SAS model

I am a bit of a SAS novice so please forgive my ignorance. I have a generalized Linear mixed model in SAS based on past data but I don't know how to export it to a pure mathematical formula that ...
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1answer
38 views

Relevance of Mixed Model Estimates vs. Observed Means [duplicate]

This question is a follow-up to a previous question I asked regarding mixed model effects construction, linked here. It provides some background, although this is a broader question with little to do ...
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11 views

OLS or GLS for balanced random coefficient model [closed]

For the balanced random coefficient model, The beta_hat is the GLS for beta, would you please help me to figure out that why it is Y_bar, where does y_bar come from. Thanks!
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1answer
22 views

'Translate' ANOVA comparison on regression parameters into linear mixed model

I am analysing data from a medication study. Participants did the same task twice; in one session they were given a certain drug and a placebo in the other one. The order of the sessions was perfectly ...
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1answer
37 views

three way interaction in lmer

I have two continuous variables (cfreq, and LanPro), and one catergorical variable (cond_aud, as shown in the picture). The summary of a lmer model shows a three way interaction of aud (EA and NoA) x ...
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29 views

Power calculations for a mixed model using simr

I'm trying to conduct a power calculation for a mixed effect model I built using lmer. I already have some pilot data, so I have an idea of the estimated effect size, but what I'd like to know is what ...
3
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1answer
31 views

How to enter confounding variables and variables competing for exposure into a mixed-effects model in lme4?

Let's imagine I am interested in the association between happiness and pain. I run a study where I ask participants to rate both ...
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13 views

Comparing variables against a baseline in R random effect mixed models

I am trying to analyse the effect of age and town on F2 value of speakers. Firstly apologies if this question is really basic, I missed pretty much all of my R tutorials due to the pandemic and having ...
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1answer
22 views

Redundant Parameters in Cross-Level Interaction: Mixed Modeling

I'm using SPSS to run a Mixed Model with two categorical (factor) predictors with an interaction between the two predictors. I get the following Estimates of Fixed Effects: In the interaction I am ...
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1answer
66 views

Two levels of a factor in a linear mixed model; one is fixed and another is random. Is that possible?

Can you specify one level of a factor as fixed and the other as random in a linear mixed model (with lmer)? Some background information first: A set of speakers who vary in their proficiency levels (...
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2answers
221 views

Linear Mixed Effects Models: how to model dependent categorical variable?

I am trying to fit a linear mixed effects model with several fixed effects and a random intercept that varies per subject. My problem is that I know that one of the fixed variables, let's call it 'A'...
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1answer
24 views

Linear mixed effect model in statsmodel package

I try to use linear mixed effect model in Python statsmodels package. However, I have no idea how to conduct and interpret the result. Group 1 (20 people) : base line & follow up Group 2 (20 ...
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1answer
25 views

experimental design - repeated measures within factor combinations?

Sorry for what might be an obvious question, but I have a question about an experimental design for which I can create a "mouse" analogue: I have 270 mice. I have 2 treatments (factors)-- L ...
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1answer
50 views

ANOVA with missing cells and multi-level analysis

I'm about to analyse some data (hypothesis testing) and would like some feedback on my approach as I have never seen this situation (missing cells in an ANOVA-like table). I would also like to know if ...

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