# random effects

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2. ### SAS glimmix overdispersion

Let's say I have an experiment with a total of 10 petridishes each with 20 seeds. 5 of these petri dishes are variety A and 5 are variety B. I count the number of germinated seeds in each dish. There seems to be to be two main ways to model potential over dispersion: proc glimmix data=a...
3. ### Mixed model regression for income by ZIP

I'm running a regression analysis to understand the impact of income (predictor variable) on scores on an instrument (dependent variable). The only problem is that I don't know each individual's income; I've estimated it using their ZIP code. I've experimented with a few different methods to...
4. ### Multi-level Meta-regression using random effect for treatment? [R pkg metafor]

I am a biostatistician consulting on a meta-analysis of 16 studies each w/ 2 treatment arms. The main interest is in the effect of the variable plateau pressure (PP from now on), on mortality rate. As there is a strongly significant difference in PP between the two arms, I do not believe both...
5. ### multilevel random effects model

I want to look at the change in the percentage of income savings measured in dollars using repeated measures data for older adults. I want to compare three groups based on their father's occupation while growing up. I want to estimate different slopes and intercepts for the three groups. For...
6. ### split-split plot with continuous subplot variable

Hello I am trying to analyze data from a split-split-plot design. The sub-plot is a continuous factor and since we suspect a non-linear relationship, the quadratic form needs to be tested as well. Factors: a-main plot-5 levels b-subplot-continuous c-sub-subplot-2 levels. To test the quadratic...
7. ### Correcting for regression to the mean in mixed effects model of longitudinal data?

Hey everyone, I know you can correct for regression to the mean for two time points, in a before and after scenario. But does anyone know how to do this when there are more than two time points, let's say there are about 10 points in a time series. I was hoping to model the longitudinal data...
8. ### Estimating fixed vs. random effects with lme (Hausman?)

I have ran two lme mixed effects models in R, both using the same fixed effects variables but each with a different random effect variable. My reviewer has said I should use the Hausman test to estimate the effect of fixed vs. random effects. On looking in to this I can only find R code for the...
9. ### Anybody knows how to specify a latent class model using FLXMRLMER in R?

Hi Everyone, I'm trying to use the package 'flexmix' in R to specify latent class models. I want to specify a model that has random effects. I looked up the flexmix package documents, and found that the function 'Flxmrlmer' could return a flexmix object that has random effects specified...
10. ### When does the Normal Distribution arise?

Hello guys, Studying the multivariate normal distribution (and the univariate one as well), I found in Muirhead (1982) that the normal distribution arises when "the observations themselves can be regarded as sums of independent random vectors or effects". Mi question is if every time...
11. ### Multilevel Linear Modelling Help

Hi, I'm hoping someone with expertise with MLM/HLM etc might be able to help me. I recently conducted a transmission chain study looking at the impact of mood on production. The study involved participants reading a story and reproducing this story for another person. The second person read...
12. ### Trouble with random factors glmm

Hi. I am doing a behavioural ecology study on juvinile brown trout and want to perform a glmm (glmer, package lme4) to analyse the effect of activity, size and treatment on survival. The variables i am using and are: response-survival (dead or alive), fixed effects- size (continuous), activity...
13. ### random effects in mixed models

Hello I am not very familiar with mixed models --- I have been reviewing the various tutorials on the web but still am not sure if/how to specify my model, even to start with. I have a relatively simple design: - two weight groups (non-random; normal/obese) -- randomized within each group to...
14. ### How to do survival analysis in SAS with interval censoring and random effects

Hi, I am interested in using survival analysis methods on seed germination data. I have just started reading Allison's Survival analysis in SAS. Accelerated failure time analysis (using PROC LIFEREG) and Cox proportional hazards models using PROC PHREG seem promising, but I have a feeling...
15. ### Correct interpretation of Lmer output

I have produced the following model lmer(TotalPayoff~PgvnD*Type+Type*Asym+PgvnD*Asym+Game*Type+Game*PgvnD+Game*Asym+(1|Subject)+(1|Pairing),REML=FALSE,data=table1)->m1 PgvnD=A percentage (numeric) Asym= a factor 0 or 1 Type=a factor 1 or 2 Game= a factor 1 or 2 from this model the terms...
16. ### Correct structuring of random effects?

Hi I have produced a mixed effects model as follows; lmer(TotalPayoff~Type+Game+PgvnD*Asym+(1|Subject)+(1|Pairing),REML=FALSE,data=table1)- each pairing contains 2 subjects and each Subject is in 2 different pairings with different subjects. Have I structured the random effects in the...
17. ### Standard Deviation of Random effect is 0?

have a model with two random effects lmer(TotalPayoff~Type+Game+PgvnD*Asym+(1|Subject)+(1|Pairing),REML=FALSE,data=table)->m1 each pairing contains 2 subjects and each Subject is in 2 different pairings with different subjects. For some reason the subject random effect has SD =0 I do not...
18. ### Fixed and Random Effects in Mixed Modeling

Thank ahead of time for any help. I am analyzing time series data. Originally I was running Repeated Measures ANOVA and entering between subjects variables. This was providing significant and interesting results. However, there is missing data, and of course, RM-ANOVA deletes listwise. I was...
19. ### interpreting random effects

I have have measured the trait frequency for a "mountain" associated allele across a number of sites and years. In my (glmer) model I have summarized the allele frequency by site and year as the dependent (binomial) variable and specified site and year as random effects. The fixed effects are...
20. ### Random effects estimator

Hi, I don't quite understand what a random effects estimator actually does... I have individual data for 2 (not adjacent) years: Some individuals were asked twice (1000 people), some only in one year (500 people). Estimating a random effects estimator with STATA results in 1500...