regression
ANCOVA
Compare adjusted group means while controlling continuous covariates.
Requirements
- continuous outcome
- group factor
- covariate(s)
Avoid when
- nonlinear covariate effects not modeled
- strong group-covariate interaction
Formula
y = β₀ + β₁·group + β₂·covariate + ε
Interpretation
Reports adjusted group effect after accounting for covariates.
Worked example
Compare post-treatment scores between groups while adjusting for baseline score.
Open example datasets