association
Point-biserial correlation
Measure association between one continuous variable and one binary variable.
Requirements
- continuous outcome
- binary predictor
Avoid when
- multi-level categorical predictor
- strong non-normality with tiny samples
Formula
r_pb = (M₁−M₀)/s · √(n₁n₀/n²)
Interpretation
Equivalent to Pearson correlation where one variable is binary-coded.
Worked example
Relate a continuous score to a genuinely binary treatment indicator.
Open example datasets