All Questions
39 questions
1
vote
1
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30
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Testing the effect of a continious IV on DV, in order to explain group differences
I would like to ask a question regarding an analysis I’m planning and it might be a basic question so, apologies in advane.... To describe the situation: There are two groups of participants in my ...
- 31
2
votes
0
answers
70
views
How well does my model fit? Specifying a null-model in non-linear mixed models
I want to fit a model y ~ b * exp(-exp(a) * x), but including a random effect, with this data:
...
- 33
5
votes
1
answer
53
views
Is repeated measures appropriate for testing for a difference in repeated paired group measurements?
I'm new to repeated measures and am trying to understand how it maps to lmer.
I have measurements from two time periods:
$t_1, t_2$.
At each measurement period, the same 50 different foods are scored ...
1
vote
0
answers
64
views
Comparing mixed effect models fitted to two different datasets
I have two different time series data which are the results of running a simulation model with different sets of parameters and configurations. The datasets each contain 100 time series which indicate ...
- 13
1
vote
1
answer
92
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I think this data should be analysed using a linear mixed-effects model, but it doesn't seem to make sense when using buildmer? [closed]
I can't give the exact data because it's sensitive, but I have the following information about the data:
3 continuous variables which are within subjects (scores for test separated by time).
1 ...
0
votes
0
answers
73
views
How to compute Cohen's d and p-value for comparison of least squares mean from two different mixed models?
I have two randomly assigned treatment interventions (A and B), and two subgroups of individuals (X and Y). This is a longitudinal study with dropout. I want to test whether the outcomes of ...
- 31
9
votes
1
answer
773
views
Confused: Why is lme4 changing techniques from Wald F tests to Wald Chisquare?
I've constructed some LMEMs that use dichotomous variables and their interactions as regressors, and I've become confused by the output. When I only assess a single interaction, using the code below (...
- 129
1
vote
1
answer
334
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Can you include between-subject control variables in random effect structure of mixed models if they are not fixed effects?
I tried finding similar cases and questions but failed and got even more confused because the answers seem to depend on when the questions were asked due to changes in the lme4 package. So I'm sorry ...
- 11
2
votes
1
answer
568
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How to interprate random effects in an lme model in R [closed]
I am having trouble understanding the results of my lme model. Could someone tell me how to understand the random effects?
Here is my model:
...
- 21
2
votes
1
answer
2k
views
Mixed effects model adding covariate vs adding random effect
I am currently looking into mixed effect models and I am trying to understand the difference between adding a random effect and adding a covariate to a linear model.
Consider this example:
...
- 27
2
votes
0
answers
451
views
How would I conduct an equivalence test in R from an lmer() model?
Lets say I have a null result, as in the following example:
library(lme4)
iris$Rand <- rnorm(150)
m <- lmer(Petal.Width ~ Rand + (1|Species), data = iris)
...
- 2,701
0
votes
0
answers
30
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What is a good model for this data?(plot attached)
I don't think a linear model would fit this? This is a change in the 'dependent' variable over trials in two conditions.
The hypothesis is that over trials the dependent variable reaches a tabletop/...
0
votes
0
answers
1k
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GLMM. Why are my confidence intervals so wide when my p-values are so small?
I am trying to find out whether there is a significant effect of Treatment (factor with 3 levels: GR, BC and WF) on the number of moths captured per night in a field experiment. I have 15 Blocks that ...
- 41
9
votes
2
answers
4k
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 ...
- 383
0
votes
0
answers
3k
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Mixed models: Assessing significance of random effects
Edit: Just adding a relevant blog post that discusses checking if a random effect should be included or not, but my question is more specifically based on deciding if the intercepts and slopes of ...
- 556
2
votes
1
answer
5k
views
How to interpret the output of lmerTest::ranova in R?
I wanted to find the p-value of the random effect in a linear mixed model. I used ranova from lmerTest.
I am not sure how to ...
- 21
7
votes
1
answer
8k
views
Satterthwaite degrees of freedom in a mixed model change drastically depending on the DV
I have a couple of MLM models created using lme4:
y1 ~ x1 + x2 + x3 + x4 + (1+x4|id)
y2 ~ x1 + x2 + x3 + x4 + (1+x4|id)
...
- 2,361
2
votes
0
answers
2k
views
Satterthwaite degrees of freedom in lmerTest for a 3x2x2 mixed model vs. mixed ANOVA dfs
I have traditionally been running my analyses using aov and would like to switch to lmer. My questions is whether or not this is ...
- 613
1
vote
0
answers
289
views
Which of the (two) conflicting p-values should I use when estimating lmer using R
I've recently started using LMM which possibly gives me better insight into my DV. Only I got some contradictory data regarding whether some variable is significant or not.
The Us and Hed variables ...
- 31
0
votes
1
answer
483
views
Significance of the control predictors in a non-significant full-null model comparison (mixed model)
The situation:
A, B, C, and D are fixed effects, and <...
- 13
7
votes
1
answer
7k
views
How can I obtain z-values instead of t-values in linear mixed-effect model (lmer vs glmer)?
I am wondering why in my lmer model the summary() only yields t-values rather than z-values, such as here:
...
- 505
7
votes
1
answer
5k
views
Big difference between a t-test and a F-test in a mixed model (anova vs summary in lmerTest)
While helping someone else with their analyses, I've run into a question regarding the difference between t-tests and F-tests for linear mixed models in lme4 for R, as provided by lmerTest. I'm aware ...
- 237
2
votes
0
answers
1k
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Linear mixed models. how to test if a condition is different from zero.
I have two conditions, A and B (see the figure below).
I want to test if these conditions are different each other, if condition A is different from 0 and if condition B is different from 0.
I'd ...
- 301
4
votes
1
answer
7k
views
Differences between summary and anova function for multilevel (lmer) model
I've been working on some multilevel models using the lmer function in R and have been playing with some different ways of testing the significance of the fixed effects of my model. I have found that ...
- 41
15
votes
1
answer
16k
views
Conflicting results of summary() and anova() for a mixed model with interactions in lmer+lmerTest
I recently came across what I think may be a problem in how the anova() function from the lmerTest packages computes its F-...
- 451
0
votes
0
answers
165
views
ANOVA comparison of non-significant mixed models
I have two nested mixed models: the difference in these models is the presence of one predictor variable (type). I used lmerTest ...
- 163
1
vote
1
answer
1k
views
lmer: comparing model fit and null hypothesis significance testing
We recently used lmer to analyze some reaction time data. There were three fixed effects variables, and the model included their interactions and a fully specified random effects structure. Something ...
- 11
11
votes
0
answers
155
views
10 % false positives from nonlinear mixed effect models : Why? [closed]
I've run a simulation study in order to estimate type I error rate of the test of group effect in a nonlinear mixed effects model, using nlmer from lme4 package. The results show there is 8-10 % false-...
- 1,043
4
votes
0
answers
336
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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 ...
- 771
3
votes
1
answer
547
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Hypothesis testing: If not a p-value in mixed effect models, then what?
I've been working on a messy, repeated measures data set of endocrine data looking at a small group of variables (after eliminating several uninteresting contenders in exploratory data analysis), each ...
- 51
15
votes
1
answer
16k
views
Comparing mixed-effects and fixed-effects models (testing significance of random effects)
Given three variables, y and x, which are positive continuous, and z, which is categorical, ...
- 1,531
1
vote
0
answers
879
views
Testing and correctly interpreting the significance of nested random effects
I'm building a series of relatively simple random effects models where we repeatedly measure a water quality variable, say conductivity (cond), in different watersheds (ws) and streams (st). Here, ...
- 101
2
votes
1
answer
1k
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Mixed effect modelling with multiple, nested random variable
Goal: comparing pitch (Hz) on three types of words
Dependent variable: Hz
Fixed predictor variable: word-type, points (measurements taken from five points on each token, to capture Hz change within ...
- 33
8
votes
1
answer
8k
views
Different p-values for fixed effects in summary() of glmer() and likelihood ratio test comparison in R
I'm using glmer() with a binomial response variable. My optimal model has two fixed effects (flow and DNA) which in summary() show a non-significant p value but ...
- 135
35
votes
3
answers
53k
views
How to get an "overall" p-value and effect size for a categorical factor in a mixed model (lme4)?
I would like to get a p-value and an effect size of an independent categorical variable (with several levels) -- that is "overall" and not for each level separately, as is the normal output from ...
- 1,345
5
votes
2
answers
5k
views
I want to use pvals.fnc() to get p-values for a lmer() model but cannot get rid of correlations between random factors
My problem can be summarized very simply: I'm using a linear mixed-effects model and I am trying to get p-values using pvals.fnc(). The problem is that this ...
- 285
4
votes
2
answers
5k
views
Contrast for hypothesis test in R (lmer)
I'm running a lmer mixed effects model with a four-level factor (levels "0","10","100","1000") as the fixed effect.
lmer(free ~ reward.f + (1|S), longdata)
I ...
- 43
100
votes
11
answers
280k
views
How to obtain the p-value (check significance) of an effect in a lme4 mixed model?
I use lme4 in R to fit the mixed model
lmer(value~status+(1|experiment)))
where value is continuous, status and experiment are factors, and I get
...
- 2,201
11
votes
2
answers
6k
views
Comparing a mixed model (subject as random effect) to a simple linear model (subject as a fixed effect)
I am finishing up some analysis on a large set of data. I would like to take the linear model used in the first part of the work and re-fit it using an linear mixed model (LME). The LME would be very ...
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