What’s the difference between Mixed and Multilevel Models? What about Hierarchical Models or Random Effects models?
I get this question a lot.
The answer: very little.
[Read more…] about Confusing Statistical Term #10: Mixed and Multilevel Models
OptinMon 21 - Random Intercept and Random Slope Models
Three Designs that Look Like Repeated Measures, But Aren’t
Repeated measures is one of those terms in statistics that sounds like it could apply to many design situations. In fact, it describes only one.
A repeated measures design is one where each subject is measured repeatedly over time, space, or condition on the dependent variable.
These repeated measurements on the same subject are not independent of each other. They’re clustered. They are more correlated to each other than they are to responses from other subjects. Even if both subjects are in the same condition. [Read more…] about Three Designs that Look Like Repeated Measures, But Aren’t
Multilevel, Hierarchical, and Mixed Models–Questions about Terminology
Multilevel models and Mixed Models are generally the same thing. In our recent webinar on the basics of mixed 
models, Random Intercept and Random Slope Models, we had a number of questions about terminology that I’m going to answer here.
If you want to see the full recording of the webinar, get it here. It’s free.
Q: Is this different from multi-level modeling?
A: No. I don’t really know the history of why we have the different names, but the difference in multilevel modeling [Read more…] about Multilevel, Hierarchical, and Mixed Models–Questions about Terminology
Is there a fix if the data is not normally distributed?
In this video I will answer another question from a recent webinar, Random Intercept and Random Slope Models.
We are answering questions here because we had over 500 people live on the webinar so we didn’t have time to get through all the questions.
[Read more…] about Is there a fix if the data is not normally distributed?
What packages allow you to deal with random intercept and random slope models in R?
In this video I will answer a question from a recent webinar, Random Intercept and Random Slope Models.
We are answering questions here because we had over 500 people live on the webinar so we didn’t have time to get through all the questions.
Can I Treat 5 Waves of Repeated Measurements as Categorical or Continuous?
Question: Can you talk more about categorical and repeated Time? If I have 5 waves at ages 0, 1 year, 3 years, 5 years, and 9 years, would that be categorical or repeated? Does mixed account for different spacing in time?
Mixed models can account for different spacing in time and you’re right, it entirely depends on whether you treat Time as categorical or continuous.
First let me mention that not all designs can treat time as either categorical or continuous. The reason it could go either way in your example is because time is measured discretely, yet there are enough numerical values that you could fit a line to it. [Read more…] about Can I Treat 5 Waves of Repeated Measurements as Categorical or Continuous?