All Questions
Tagged with mixed-model hypothesis-testing
156 questions
4
votes
1
answer
506
views
AB testing with underlying segments in population
I run ab tests with the variants applied to multiple segments, say, countries. In each country, my baseline target is very different from each other.
I wonder if I should ideally model these countries ...
- 521
3
votes
1
answer
132
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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
1
answer
982
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 ...
- 207
3
votes
0
answers
165
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Is there a joint test of model coefficients, effectively testing for main and interaction effects in quantile linear mixed model?
I am just reading this paper: Linear Quantile Mixed Models: The lqmm Packagefor Laplace Quantile Regression. Let us assume I have a repeated observation experiment, where I want to assess the effect ...
- 123
17
votes
3
answers
2k
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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
2
votes
2
answers
493
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Working with Discrete-Time Survival Analysis with Random Factors in R
I'm working with some data on artificial (fake) bird nests, looking into their 'survival' from animal attacks. I visited the nests once every two days, for 2 weeks (so my time points are 2,4,8,10,12,...
- 41
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 ...
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/...
3
votes
2
answers
99
views
Testing changes in echocardiogram wave before and after treatment
I saw a couple of questions, very similar but unfortunately without any answer e.g.here and here. I aim to make it clear here with a dummy data hopefully, to receive some guidance
I would like to ...
- 1,158
0
votes
0
answers
18
views
Testing if a regression coeffiecient is larger than another coeffeiceint [duplicate]
How to formally test whether a coeffeicent in a regression problem is bigger in magnitude then another coefficient? Here is the model (random effects model):
\begin{align}
\mbox{effeciency} = \...
- 131
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
4
votes
2
answers
6k
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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 ...
0
votes
1
answer
110
views
Linear Mixed Model using R - what is the syntax when there are within-subject variables of both fixed and random nature? [duplicate]
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 ...
5
votes
1
answer
2k
views
Power Analysis for glmer using simr
I'm trying to run a power analysis based on pilot study. I'm using a glmer mixed effects model with a binomial logit link. The model's equation is:
...
- 382
2
votes
1
answer
1k
views
Which statistical test : Anova or T-Test for between subject experiment (repeated measures ) with one IV with two levels( control and treatment)
It's a between-subject design with a control group and a treatment group with 50 people each. Each participant undergoes 100 trails. (repeated measures). So the only within-subject factor is the ...
- 71
3
votes
1
answer
202
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Statistical testing on discrete time series data?
I am trying to analyse some data which has 40 different subjects, 1 categorical factor with two levels (20 male and 20 female). The rate of tree cutting was recorded at 4 different time points for ...
- 125
6
votes
1
answer
372
views
How to test for statistical significance with multiple visits and technical replicates?
I have a data set with 100 columns that's divided between 40 normal columns and 60 MI columns. Samples from each patient were taken at two separate visits, and each sample has two technical ...
- 71
2
votes
1
answer
384
views
Hypothesis test of two population means with correlated observations
I'd like to run an A/B experiment where my outcome measures are conversion rate, and mean spend. I'd like to use two proportion Z-test and z-test of two population means, however many users in the ...
- 382
3
votes
1
answer
66
views
What type of statistical analysis to perform?
I have an experiment with 10 subjects.
Each of them has to exert force and real-time feedback is received. Each subject experiences all 3 types of feedback (within-subject factor).
Moreover, each ...
- 60
1
vote
0
answers
26
views
Fit one model or several models to maximize power for significance testing of slopes in a factorial design?
Problem
I need to perform a power analysis for a set of statistical tests. Each test is about a regression slope computed in a cell of a factorial experiment design. To minimize the required sample ...
- 76
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
1
vote
2
answers
338
views
Mean Comparison test for 3 related samples
I have ratio scale data for 3 related samples. What is the statistical test that I can use to check whether there's any significant difference between the 3 groups? (I tried Friedman, but I'm doubtful ...
2
votes
1
answer
56
views
Statistical significance testing when distributions are paired, but samples are not
I have a situation like the following:
5 distributions A, B, C, D, E of unknown type from which I can take samples to estimate the mean.
I apply an intervention or treatment to all of the ...
- 23
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
4
votes
1
answer
772
views
3x2 within subjects design with covariate that is nested within factor (?)
I want to test the differences in my interval-scaled dependent variable - measured at three time intervals (within subj.), for two conditions (within subj.), while accounting for a interval-scaled ...
- 41
0
votes
1
answer
189
views
Control variable with different levels in Regression
I have an experiment with two conditions: Control and treatment groups. I am measuring how confident the treatment groups felt while answering the question. It is a three level indicator- not sure, ...
- 71
2
votes
1
answer
151
views
Random effect or not?
My intent is to model plant growth with a generalised linear mixed model. Let's say I sampled growth of 10 plants each on 10 plots in five different (non-consecutive) years. In order to find out which ...
user45065
2
votes
2
answers
573
views
Interpretation very small standardized coefficient beta
In one of my studies I have results similar to the below:
β=-0.0007 (95% CI: -0.0009, -0.0002), p=0.01
Since β is so small (but also the Confidence Interval (CI)), is this result still meaningful?
...
- 51
2
votes
2
answers
2k
views
t-test/regression - how to account for random effects? [closed]
I need your help on how best to test the following hypotheses in R. Each observation in my data has RaterID and RaterGender, ...
- 715
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
0
votes
1
answer
220
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 ...
- 19
2
votes
1
answer
39
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 ...
- 151
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
1
answer
195
views
Confusing main effect in mixed design ANOVA
I am conducting a mixed design ANOVA test using ezANOVA. I ran two different tests as follows:
Test1: within subject variable w, between subject variables age and x1.
Test2: within subject variable ...
- 535
1
vote
1
answer
7k
views
Statistical test for paired data at multiple time points?
I have paired data (right and left measurements from the same subject) taken at different times. For the sake of the argument let's say the dependent variable (y) follows a normal distribution and we'...
- 857
5
votes
1
answer
202
views
Scientific source for why reporting p-values of random effects is not meaningful?
I have read a lot about why most statistical packages do not report the significance test results of random effects (e.g. here)
Is there any publication about this precise topic that I could use to ...
- 415
0
votes
0
answers
30
views
Aside from switching to a Bayesian approach, how can I quantify the strength of evidence for a null result of a linear mixed effects model?
I've run a linear mixed effects model with a null result that would be quite interesting for the field. Is there a test I can run that would bolster the claim that the two groups are indeed equivalent?...
- 2,701
0
votes
0
answers
3k
views
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
1
vote
0
answers
121
views
R or Stata shortcut to significance test interaction term including restricted cubic splines?
I fit the following model in R using the lme4 package, which is a linear mixed effects regression of outcome "WT_abs_change" (absolute weight change) on various factors, including "ns(WT_dtime, df=3)*...
0
votes
0
answers
57
views
How to use bootstrap to do a hypothesis test in mixed models
I have a mixed model with multiple covariates. I want to test if some of the covariates are insignificant. Since I have mixed model the LR-test will result in a p-value which is too low, hence I want ...
- 11
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
0
votes
0
answers
134
views
Random Effects ANOVA with test for difference in variances
Say I have a study measuring a continuous endpoint for 3 sample assays on two days, i.e. before and after intervention. The measurements are performed several times by different people (repeated ...
- 11
7
votes
1
answer
8k
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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
1
vote
1
answer
1k
views
Bootstrapping coefficient p-values under null hypothesis in case-resampling regression
I am fitting a multiple linear mixed-effects regression model in lme4. The residual fit is near-linear, enough to warrant not assuming residual homoscedasticity. ...
- 219
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