All Questions
Tagged with mixed-model hypothesis-testing
31 questions
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
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
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
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
29
votes
2
answers
15k
views
How should mixed effects models be compared and or validated?
How are (linear) mixed effects models normally compared against each other? I know likelihood ratio tests can be used, but this doesn't work if one model is not a 'subset' of the other correct?
Is ...
- 2,842
17
votes
3
answers
2k
views
Should "City" be a fixed or a random effect variable?
I am analyzing data on "BloodSugar" level (dependent variable) and trying to find its relation with "age", "gender" and "weight" (independent variables) of ...
- 10.2k
4
votes
1
answer
262
views
What kind of model is best suited for this type of data and research question?
I have data for hundreds of individuals over several (often tens) of years. My dependent variable is a binary event that may or may not have happened for each individual in some given year. The event ...
- 73
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
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 ...
- 183
10
votes
4
answers
9k
views
How to test random effects in a multilevel model in R
I have been reading a good book called Applied Longitudinal Data Analysis: Modeling Change and Event Occurrence by Judith Singer and John Willet. The book shows that by modeling in 2 levels, we can ...
- 517
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
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
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
5
votes
1
answer
555
views
Paired and repeated measures! Now what? ANOVA or mixed model?
I have a simple setup. I have 10 patients and I would like to test the effect of a certain drug on kidney function. Each patient will serve as his own control and intervention.
First for the control ...
- 85
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
0
answers
336
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 ...
- 771
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
4
votes
2
answers
6k
views
Linear mixed model in R; modelling fixed effects with multiple levels and interactions. Help!
I am new to R and to mixed linear modelling. I have a dataset with variables from a cross-sectional study looking at fractional anisotrophy (a property of the brains white matter) in 6 different white ...
3
votes
1
answer
696
views
Understanding Mixed Effect Models visually with some questions on P-value calculations
I've been tackling the concept of Mixed Effects Models on and off for the last 9 months. Every time I would give up and come back later to try and understand it again with my basic statistics ...
- 145
3
votes
1
answer
132
views
Is it possible to test for strongest predictor, if all variables are identical within a random effect grouping?
I'm trying to understand the regression analysis done in a published study.
They use GAM models to predict plant growth, and to test for the most important predictors. They have measured growth of ...
- 1,118
2
votes
0
answers
71
views
Hypothesis testing : Constant mean over time for two conditions within an experiment
What is an approach to testing/showing that within a particular period of time, there is no change in values. So, I have my response variable measured over 30 seconds, in two conditions. I want to ...
2
votes
1
answer
224
views
How to simulate type I error for random-effects model?
Building upon this post How to simulate type I error and type II error. I would like to simulate type I error for a random-effects model I generated. The statistic of interest is standard deviations ...
- 211
2
votes
1
answer
92
views
Which test would take advantage of comparing large sample groups with replicates?
So, the data is comparable to height of individuals within Africa and Europe, but each group (Europe, Africa) have multiple replicates (3 x month sampled).
Each replicate is ~100,000 individuals.
A ...
- 21
2
votes
1
answer
1k
views
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
2
votes
1
answer
220
views
single time series per participant and using random effects in mixed effect modelling
My mixed effect model design involves assessing 42 different time series via a polynomial function. that is, fixed effects of time and time^2. I've incorporated a random slope of the individual time ...
- 217
2
votes
0
answers
135
views
Identifying when fixed effects have changed in a GLMM
I have a dataset spanning several years, that I have analysed year by year (using the same glmm model code) to determine whether the random effect (random intercept) has altered over time. I have ...
- 3,952
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
2
votes
3
answers
524
views
How can I test whether two logistic regression coefficients are identical in mixed models?
Similar to question here.
3 variables (1 continuous (X) and 2 categorical (A & B)) predict 1 dichotomous variable in generalized linear mixed models.
Both variables A and B are dichotomous and ...
- 1,782
2
votes
1
answer
911
views
How can I test whether two logistic regression coefficients are identical?
3 variables (1 continuous (X) and 2 categorical (A & B)) predict 1 dichotomous variable in logistic regression.
Both variables A and B are dichotomous and are coded with 1 (reference category) ...
- 1,782
1
vote
0
answers
90
views
What statistical test is appropriate to answer hypotheses on seasonal and spatial differences?
First of all, I am very new to statistics, so this might be a very basic question but I could not find any answers to my question in other topics here.
I have a data set on microbial growth (...
- 11
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