association
Pearson correlation
Measure linear association between two continuous variables.
Requirements
- two continuous variables
- rough linear pattern
Avoid when
- ordinal variables
- strong outliers
- curved association
Formula
r = cov(x,y) / (sₓsᵧ)
Interpretation
r ranges from -1 to 1; p tests r = 0.
Worked example
Estimate the linear association between age and systolic blood pressure.
Open example datasets