ANCOVA Flashcards
What is an ANCOVA?
A one-way ANOVA which takes a covariate into account (e.g. a confound)
What is an F ratio?
experimental variances / random variance
What does adding a covariate do to the significance?
It can either increase or decrease a result
What should the pie look like to have a significant finding?
The covariate and explained variance should be similar in size and bigger than random variance?
Why should you use estimated marginal means (EMM)?
- Covariates influence the DV and we want to get rid of that effect
- EMMs are adjusted using the covariate
Why does the significance of the analysis increase when the differences between the means decrease?
Because the random variance is reduced, we can be more confident of the differences we find
What kind of data should covariates be?
Continuous and binary variables
Can you use variables with more than 3 categories?
Cannot be easily analysed, need a complex dummy variable modelling
When do you include a covariate?
When it is well justified by research
