random effects

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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...