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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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Simple effects in mixed design with R

My experiment consists of two factors, one between and one within subject. Time is the between-subjects factor and hold two levels: (low and high). Times is the within-subject factors and hold three ...
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11 views

Linear mixed model for repeated measure in R [on hold]

I've been struggling to find right measures for my study. I treated my patients with drug A and placebo, and measured FEV1 in 4 different time. I regarded treatment and time as fixed effect, and ID ...
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How can we calculate all models possibilities for a negative binomial mixed model? [on hold]

Our problem here described is to obtain the best model from a GLMM negbin. Our data compose by 2 Categorical variables (Yes/Not), 3 Numerical variables and our random factor, all without any NA. We ...
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Planned contrasts in mixed models

My experiment consists of two factors, one between and one within subject. Time is the between-subjects factor and hold two levels: (low and high). Times is the within-subject factors and hold three ...
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0answers
13 views

Interpreting interaction effect between two categorical predictors using linear mixed model

I have read other threads regarding this topic, however, I haven't come across a results table that looks similar to mine (below) so I am seeking some clarification. I am using MIXED (SPSS v25) to ...
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1answer
28 views

r-linear mixed model with the random effect variable be continuous

Suppose there are $N$ subjects under study, with subject $i$ contribution $n_i$ observations, for $i =1,...,N$. And let $y_{ij}$ denote a response variable for subject $i$ at observation $j$. Let $x_{...
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21 views

allEffects-Interpretation and missing p-values

I need to run a logistic regression with random effects, about wheelchair users and hinderance due to environmental barriers: ...
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34 views

Is lmer or glmer appropriate for nested continuous proportion data

I have a reviewer that wants me to analyze my data along the lines: Con_Ratio ~ Range * Latitude * Longitude + (1 | Genotype/Pair). But I'm not sure if this can be done and how. My experimental ...
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6 views

Nested models and ANOVA: F ratios

I have some commuting data involving a factor B (district) that is nested inside another factor A (city). I am assuming both factors are fixed. I have calculated F ratios involving $MS_A/MS_R$ and $...
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1answer
47 views
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Handling baseline differences with a retrospective study and mixed model

I am looking at the fixed effects of Var1, Var2, and Var3 on a dependent variable ...
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1answer
50 views

The form of the Log-Likelihood Function in Mixed Linear Models

Let us assume the following mixed effects model: $y = X\beta+Zu+e$ where $y$ is a vector of n observable random variables, $\beta$ is a vector of $p$ fixed effects, $X$ and $Z$ are known matrices, ...
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Why is it so hard to find straightforward explanations for the use of GLMs and MEM? [closed]

We all know that for tests like ANOVA, T test, Wilcoxon, Kruskal-Wallis it is easy to state the conditions unto which we would be able to apply them. Examples: ANOVA: several groups, one variable, ...
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which test to use

I'm wondering which statistics should I use. I’ve conducted an acceptability judgment task using 7 point scale for 8 different conditions. My study has a 2*2*2 factorial design with two level for each ...
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Incorporating uneven sample sizes into linear mixed models

I have run an experiment measuring behaviour of individual animals of different Species. Given that the species are all quite different, I standardised my experiments by biomass, but this means that ...
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1answer
37 views

Which random effects to include in a mixed effects model?

I am analyzing data from a perceptual decision making experiment (10 participants, 1800 trials each). Participants made perceptual decisions (3 possible responses) and then rated their confidence on a ...
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11 views

R: Why does my Expectation-Maximization estimation for bimodial distribution give the wrong cutoff value? [closed]

I am putting together a regression model with data of carseat sales from the ISLR dataset. It is sales as a function of the independent variables. One of the variables has a bimodal distribution ...
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21 views

How do I Identify a cutoff value from bimodal data?

I am putting together a regression model with data of carseat sales from the ISLR dataset. It is sales as a function of the independent variables. One of the variables has a bimodal distribution I ...
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0answers
22 views

Generalized linear (mixed?) model with imbalanced nested data

I am unsure how to optimally model a data set obtained from a crude experiment to compare performance of two plastic molding tools used to manufacture widgets. Widgets are tested and results are ...
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2answers
34 views

“Mixed model ANOVA with random effect”--is this the correct analysis?

Question about an analysis that was done for a study I'm reviewing: The study compared two methods of taking patient core temperature around surgery at a single center; Apx. N=200, temp was taken for ...
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1answer
24 views

finding outliers in mixed model [duplicate]

I'm trying to find outliers in this mixed model: m1 <- lmer(y ~ service + lectage + studage + (1|d) + (1|s), data=InstEval) So I used the ...
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Different model result with log-transformed vs. original dependent variable in linear mixed model [duplicate]

I fit my data with linear mix model using y and log-transformed y like below: ...
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0answers
27 views

adding nuisance covariates to mixed-model [duplicate]

I have a mixed-model with several predictors of interest and I also collected additional nuisance covariates that are not really interesting but which I would like to control for in my model. For ...
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1answer
43 views

reporting regression results with categorical variables and interactions

Several sources recommend reporting regression coefficients in a table for every mixed-effects model. For continuous predictors that's fine because I only get one coefficient for that predictor. But ...
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1answer
34 views

Extremely large difference in AICs between two models

I am currently fitting a mixed model where I analye longitudinal trends in migration between country pairs (68335 observations nested in 6442 groups). One of the first questions I wanted to have ...
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What statistical to use - variability between but not within

I have a data set where each line represents a participant's response to a series of questions (e.g., attitudes towards democracy, life satisfaction). Participants were recruited from different ...
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14 views

Mixed effects model - use dummy variable to correct to reference/standard? [closed]

I'm doing a mixed effects model that can be described generically (I'm doing a chemistry problem) as such; House price varies with distance from the centre of town. I'm fitting this as a quadratic ...
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1answer
81 views

Setting up contrasts in lmer?

0 I have 139 subjects (ID), with measurements taken at two time points (Time1, Time2), at 148 brain regions, a dependent measure called volume, and a covariate called thickness. Each subject has 148 ...
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non-parametric tests for repeated observations

I am looking for an RM-ANOVA alternative that fits with non-normal data that may not satisfy sphericity assumption. My dataset: Through a mark and recapture study, I trapped turtles, and collected ...
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1answer
85 views

Model interpretation lmer?

I have 139 subjects (ID), with measurements taken at two time points (Time1, Time2), at 148 brain regions, a dependent measure called volume, and a covariate called thickness. Each subject has 148 ...
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1answer
53 views

Curved regression lines

I had already asked a similar question here, but I'm experiencing the same problem for a different data-set and for a different family of mixed models. My response variable is a binary outcome of ...
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1answer
18 views

Analyse variation between distribution curves according to factors

I have a set of continuous distributions representing the leaf area density found at different heights through a forest canopy. e.g. like that found in Whitehurst et al. (2013): For each of these ...
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1answer
48 views

Linear mixed model for placement of nuclear stress in 10-word turns

I'm trying to model the placement of nuclear stress in 10-word turns in a linear mixed model but am very new to mixed modeling. The model includes these variables: ...
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84 views

Mixed-effects logistic regression

I'm new to data analysis and I'm trying to perform a mixed-effect logistic regression. My data look like this: ...
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2answers
54 views

What is the Joint Density Function of a Three-Level Mixed-Effects Model?

This is a follow-up question to a question I posted earlier. Obviously, maximum-likelihood estimation of mixed-effects models requires the joint density function. Let us assume a two-level mixed ...
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1answer
38 views

How to control for age in analyzing longitudinal data using mixed effects regression

I am analyzing a longitudinal dataset. Elderly subjects perform a cognitive test once a year, for five consecutive years. I want to know if there is a decline in their performance through the study ...
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2answers
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Interpreting linear and polynomial predictors in LMM

I am using linear mixed models to investigate change over time on the score on a questionnaire, which was administered at 5 points in time. While I hypothesized a decline, I had no a priori ...
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Random effect implicitly nested in a fixed effect

In a very lucid and informative answer to a question about nested versus crossed random effect (posted on 8 August 2016) Robert Long used a classes within schools example to illustrate the syntax to ...
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1answer
44 views

Select mixed model same degree of freedom

When I have a two mixed models (lme function) with different df then ANOVA summary shows the p-value of likelihood ratio test as following : ...
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1answer
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Chi-square test with replicate nested

I have a question about how to analyse count data with replicates nested in each treatment. For example, imagine temperature can influence the sex ratio of mosquito larva emerged from eggs. I have two ...
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1answer
71 views

Mixed Models: How to derive the mixed-model equations?

In the context of best linear unbiased predictors (BLUP), Henderson specified the mixed-model equations (see Henderson (1950): Estimation of Genetic Parameters. Annals of Mathematical Statistics, 21, ...
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1answer
73 views

Can one usefully specify a multilevel-model with a partially-nested, partially non-nested structure?

Background Gelman and Hill's Data Analysis Using Regression and Multilevel/Hierarchical Models includes an example in section 13.5 of how to model non-nested data. The second example in this section ...
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1answer
53 views

Can I used a General Linear Mixed Model when there are repeated observations for only a small proportion of cases?

I am trying to make a model with a response variable of performance on a test (interval data), along with predictors for test performance. It's a threshold test, so anyone that passes it will not have ...
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1answer
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Nested design with “lmer” function

I have a nested data which I cannot model properly. The data satisfies all the assumptions of ANOVA. Data description: 4 varieties of plants planted in 4 blocks and in each block the same variety has ...
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1answer
38 views

Presentation of mixed model results

I have been supporting the statistical assessment of a clinical study in which we have used a mixed models approach. For reference, the study looked at the error in subjects pointing at different ...
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1answer
11 views

Analyzing multiple repeated measurements from same individuals under different conditions

I have 4 participants who are exposed to two different environments A and B and their skin temperature is measured every 10 minutes for 1 h. Hence there is 7 measurements per one experiment (0min, ...
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2answers
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controlling for clustering at id level in mixed effects model

I have one group ($n=40$) of subjects pre- and post-tested (time; coded $0$ and $1$) on a continuous variable (y). I also have a ...
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1answer
25 views

What type of Mixed Method is this?

Really confused about this as have never done a mixed methods study before. The study in a nutshell – participant does brief test battery, then is interviewed for 15 mins. Some interview questions ...
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1answer
50 views

Lmer set up for repeated measurements?

I have 139 subjects (ID), with measurements taken at two time points (Time1, Time2), at 148 brain regions, a dependent measure called volume, and a covariate called thickness. Each subject has 148 ...
1
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0answers
23 views

lme4 syntax for random effect nested under fixed and random effects

I have data looking at the performance of thousands of one-vs-all binary classifiers trained for an image recognition task under different conditions. I'm trying to use ...
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0answers
16 views

interpretation of treatment effect from linear mix model when Y is log-transformed in longitudinal analysis

In a clinical study, 100 patients are evenly divided into two treatment group, trtA and trtB. For each patient, a biomarker is measured at 5 different visit timepoints. Y is the measured biomarker ...