# mixed models

1. ### modeling ratio between test response and control response in a repeated measures design

Hello everyone ! I am currently struggling with the analysis of a repeated measures model. Data are organized as follow: Each subject has received a particular vaccine. The blood of each subject is then tested with different viruses. Three quantitative measures are made for each couple...
2. ### Multiple Imputation in SPSS: What to do and report

Hi everyone :) I'm currently working on a research question where there are 2 categorical predictor variables (one with 2 levels between subjects, the other with 7 levels within subjects) and one continuous response variable. I want to conduct a simple repeated measures ANOVA in SPSS. The...
3. ### Generalized linear mixed model, continuous variable, zero values

Hello, I have conducted a longitudinal study with four waves of data collection. My data have a nested structure: there are four levels in my data (time - level 1, student - level 2, class - level 3, school - level 4). Student sample size = 51 (no missing values) I want to fit generalized...
4. ### Multilevel modeling with small N and large number of observations

I'd like some general help figuring out which statistical approaches might be useful for my current situation. I'm working with: A sample of 9 subjects; id A 'time' variable (measured in seconds [0...~15000]) consisting of about 15,000 observations per subject; time A continuous dependent...
5. ### R squared for linear mixed models

I have a large dataset with longitudinal data from patients with repeated measures and unbalanced timepoints. The dependent variable is level of protein and I have several fixed predictors. The best fitting model Is a linear mixed model which is a random intercepts and slopes model. The random...
6. ### Mixed Model Analysis SPSS

Hello All, I have a data set which I am trying to find out what is the best way to go about analyzing. I have been asking around and was advised that mixed model is the best way to go. Basically, this is a brief explaination of my data set. I am trying to see the efficacy of Drug X on tumor...
7. ### Market Mix Models : Confidence in Coefficients

In market mix models, my sales(y) depends on 4 promotions(p1--p4). Let (b11, b21, b31, b41 ) be the coefficients of p1--p4 in one iteration and (b12, b22, b32, b42 ) be the coefficients in the second iteration. I check the validity of the model based on some general guidelines:(i)b1--b4 should...
8. ### Time-varying covariates in linear mixed models/multilevel models

Hi! I am a Norwegian phd student exploring the effects of nocturnal road traffic noise exposure in children. One of the research questions is whether noise exposure at different ages (3, 5, 7, 8 years) is associated with body mass index measured at those same four ages (does the association...
9. ### GAMM plot??

Hi everyone, I would like some help. I did a multilevel analysis using GAMM from mgcv package and plot the predict values with the confidence intervals. I read in a few foruns that the plot only use the fixed part from the equation to predict the values used in the plot. Could anyone knows...
10. ### Repeated measures ANOVA vs. Mixed Models

Hi, I'm trying to analyze the results of my Master Thesis with SPSS. I've 3 experimental conditions (factor: Group) and for variable A every subject in each condition has 2 expressions (factor: Hemisphere). I want to test the effects of these 2 factors on my dependent variable A. What I...
11. ### SPSS Mixed Models - Repeated factorial design

Hi all, I am having a lot of trouble finding any instructions or help with my analysis and was hoping someone here might be able to point me in the right direction. My experiment involves making a verbal rating at the end of each trial of a visual stimulus. There are two properties of the...
12. ### Mixed Model Regression in SPSS

Hello, I have a random group of participants that answered questions on a survey regarding their general opinions on specific health activities. Each participant answered questions about 4 randomly selected health activities (Swimming, brushing teeth, etc.). My dependent variable is days...
13. ### Proc mixed

Hello all, I am a wee bit confused about the random statement in PROC MIXED, I thought maybe you can clarify it for me in simple words. Let's for the illustration say I have an outcome variable Y, and a treatment variable X, getting: 1 - New intervention 0 - Control (or placebo in...
14. ### 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...
15. ### Generalized mixed model question

I have version 21 of spss with advance statistics. I was trying to use the generalized mixed model function, but it's not showing up in my options. I called IBM who agreed I have the correct license to enable this function, but they could not tell me why it's not showing up in my software. Does...
16. ### Mixed models, Repeated Measures, multiple DVs, SPSS- help!

Hi there, My data is approximately as follows: 400 participants split over 2 interventions. The participants are school students from 14 different schools so we want to use mixed models to allow for this nested data. The pp's were measured on 4 attitude items both before and after the...
17. ### Model not running when using lme4 - "Error: unexpected symbol..." message returned

Hi all, I have been attempting to run the following model in the lme4 package in R. mod1<-glmer(perc~treatment+region+stage+treatment*stage+region*stage+(tub+aquarium), weights=no start, family=binomial, data=data) But continue to receive the following error message: >...
18. ### Fixed effects and SPSS

Hi all, For my bachelor thesis I have to calculate the sum of some betas (betas of x1, x2, and x3) of a linear regression model with fixed effects using SPSS 19 (STATA is only used in master degree). It is the following model: y = x1 + x2 + ... + x6 + time dummies + fixed bank effects y...
19. ### How to do Regression with many replicates of y at each level of x?

Hi follows, I have data that looks as follows: X, y1, y2, y3, y4 0, 54.241, 127.728, 127.73802, 127.73802 31, 65.132, 127.729, 127.73787, 127.73792 59, 65.364, 127.729, 127.73782, 127.73789 Where y1-y4 are just independent...
20. ### Linear Mixed Models in SPSS: why the extra repeated measures option??

Hi all, I've got a basic question about the interface of SPSS linear mixed models. The initial window provides the option to designate one or more variables as "repeated measures" and to choose a separate covariance structure for these. I noticed that not using this option doesn't do an...