mixed effects models

  1. P

    Computing sequential time variable- Long format

    Hi Everyone, I am currently looking at lung function decline/change over time. Lung function parameters such as fev1, fvc, fev1/fvc have been converted to z-scores . The data is in long format with each individual having more than 2 assessments until 4. Thus, each individual has data in 2...
  2. W

    mixed-effects models with (g)lmer in R and model selection

    Mixed-effects models are wonderful for analyzing data, but it is always a hassle to find the best model, i.e. the model with the lowest AIC, especially when the number of predictor variables is large. Presently when trying to find the right model, I perform the following steps: 1) Start...
  3. N

    Specfiying fixed and random factors using Linear MIXED model in SPSS

    Hello all, I'm a bit stuck at specifying my model using MIXED in SPSS (to account for the non-independence of data/MLM structure). My goal is to figure out the levels at which the different data sit so that I can run the most appropriate model. Here's a description of the setup/data...
  4. victorxstc

    Binary mixed-model logistic regression using lmer() of lme4 for multilevel analysis

    In my experiment, each patient has been observed twice, once using placebo and the other time using the real treatment. I want to assess the predictive effects of the treatment and patients' demographics (age, sex, etc.). Therefore I have for example 100 patients, but actually 200 pairs of...
  5. P

    detecting a variance trend in random effects

    Greetings I have a measurements on grouped individuals. There are approximately 100 groups, and approximately 500 individuals per group, with measurements taken over 5 years. There are no repeated measurements. The data are observational. The outcome is binary and there are 5 candidate...
  6. J

    longitudinal mixed model troubles

    I have growth data for 5 time points. In my unconditional model the quadratic trend best fits the data (likelihood ratio test). However, the random effect for the quadratic term is not significant but the fixed effect is significant. I also have trouble when adding covariates - the g matrix is...
  7. M

    Use of linear mixed models for within subjects repeated measures experiment

    Hello, I am trying to argue that I used the correct statistical test for a paper that is currently in review. I have formulated a counter-argument, but I'm not an expert so I wanted to make sure I am correct. In my experiment, I measured how long it took for subjects to complete a task...
  8. jpkelley

    GLLAMM in R

    Hi all, I seem to recall that some of you (spunky, Dason, and other) might be doing research using latent variable models and their variants. As I start to ask more questions about the temporal sequences of signaling, aggression, and courtship in my experiments on birds (and now spiders)...
  9. A

    Mixed effects modelling

    Hey all, Im building a linear mixed effects model of a variable, lets say the headway time maintained by drivers in car following situations. I want to use a training dataset to come up with a linear regression model and validate this model by running it through several sets of validation data...