11 - Mixed Models, Multilevel Models, Random Coefficient Regression Models, Hierarchical Linear Modeling, ... Flashcards
What data types are commonly used in mixed models?
Nested data, repeated measures, longitudinal data
If you have one or more independent variables but they are measured for the same group at a single point in time, what regression method should you use?
Multiple Linear Regression
What are fixed coefficients?
Intercepts/ slopes that are assumed to be the same across different contexts.
What are random coefficients?
Intercepts/ slopes that are allowed to vary across different contexts.
Do Ordinary Least Squares Regression Models use fixed or random coefficients?
Fixed
What is the difference between marginal and conditional R^2?
Conditional includes variance explained by fixed and random effects. Marginal includes variance explained by fixed effects only.
Does the error account for fixed or random effects?
Random
What is Interclass Correlation?
A measure of the consistency of the data across clusters/ groups.
What is the range of values for ICC? Explain them.
0 - 1. 0 indicates no consistency, 1 indicates full consistency.
What R function do you use to run Mixed Effects Models?
lmer() from lme4 package
What are the fixed and random effects in: lmer(y ~ pred + (1| pred2)?
- Fixed effects: pred
- Random effects: (1|pred2)
How do you specify random effects in R - lmer()?
You add it in parentheses in the lmer() function. Arguments:
- Specification of the random effects
- “|”
- Grouping factor
What is LogLikelihood?
A measure of how well a model fits the data
What are the assumptions for Mixed Models?
- Linearity of the Model
- Normality of Residuals
- Multicollinearity
- Influential Data Points
- Independence
