association
Eta correlation ratio
Measure association between a continuous variable and a categorical grouping variable.
Requirements
- continuous outcome
- categorical predictor with 2+ levels
Avoid when
- both variables continuous
- need direction of a binary contrast
Formula
η = √(SS_between / SS_total)
Interpretation
Eta ranges from 0 to 1 and describes between-group separation.
Worked example
Quantify association between clinic category and a continuous waiting time.
Open example datasets