Spearman Correlation
A non-parametric measure of the strength and direction of the monotonic relationship between two variables.
What is Spearman Correlation?
Spearman's rank correlation coefficient (rho) assesses how well the relationship between two variables can be described using a monotonic function (as one goes up, the other goes up, though not necessarily at a constant rate). It operates on the ranks of the data values rather than the raw data itself, making it robust to outliers and non-normal distributions.
Why Spearman Correlation Matters
It provides a valid alternative to Pearson correlation when data are ordinal, skewed, or when the relationship is monotonic but not strictly linear.
Example
A sociologist uses Spearman correlation to assess the relationship between socioeconomic status ranking and subjective well-being ranking across different neighborhoods.
Common Mistakes
- Using Spearman when the data is perfectly suited for Pearson, thereby throwing away detailed continuous information and losing statistical power.
- Interpreting it as a measure of linear relationship rather than monotonic relationship.