covariance structure

  1. M

    SPSS Linear Mixed Model repeated covariance type

    Hi everyone, I need your help with regards to specifying repeated covariance type in SPSS. I am trying to build a Linear Mixed Model in SPSS with the subject being 'borough' and repeated variable being YEAR . My dependent variable is the number of people claiming housing benefit, per year (for...
  2. P

    Linear Mixed Model not displaying values in Fixed Effects table

    I am running a linear mixed model for a repeated measures design, because of some missing data, with several fixed effects and a subject random effect. I am testing several different covariance structures for the repeated measures, and in some cases there are values missing (i.e. DoF and...
  3. M

    Covariance structure in a longitudinal study

    Hi We are conducting a pharmacological trial with repeated measurements of the drug concentration in the blood over several weeks. Due to the imprecision of the method analysing the drug we have small concentration values even before administering the drug (time 0). The problem is that these...
  4. M

    Power analysis in a repeated measures desgin

    Hi We are planning a randomised clinical trial treating patients with either an active drug or placebo in 20 weeks. We measure the dependent variable several times during the study and want to evaluate the efficacy of the drug at week 20 in respect to placebo. The analysis will be within a...
  5. R

    unable to make model Hessian positive definite - help!

    Hello all, My first time posting here, and really hoping that someone can help me out! I have data from a repeated measures experiment in which the time points were not evenly spaced + some missing data from individual animals, so I am using proc mixed and attempting to find the appropriate...
  6. R

    repeated measures + SAS + covariance structure

    Hello, My first time posting here, and really hoping that someone can help me out! I have data from a repeated measures experiment in which the time points were not evenly spaced + some missing data from individual animals, so I am using proc mixed and attempting to find the appropriate...
  7. N

    Advice in Generalized Linear Models (Toxicology Study)

    Hi all, I’m new here, and fairly new to GLMMs. I’m using PROC GENMOD to model a count outcome (number of offspring) in a toxicology study. Offspring count data were collected in 10 equally spaced time points for every individual (subject) in the experiment. Besides “time”, I have a nominal...
  8. K

    Covariance structure question for mixed model repeated measures ANCOVA

    I'm working on a mixed model repeated measures ANCOVA and am working on identifying the covariance structure for my model. I am interested in modeling 2 of my variables as repeated measures, and am wondering if this is even possible. I'm working in SAS, and keep getting error messages telling me...