Spearman's Rank Correlation is a statistical method used to measure the strength and direction of the association between two ranked variables. Unlike Pearson's correlation, which assesses linear relationships, Spearman's focuses on the ordinal ranks of data, making it suitable for non-parametric data or when the relationship is not linear.
The Spearman correlation coefficient, denoted as ρ (rho), ranges from -1 to +1. A value of +1 indicates a perfect positive correlation, meaning as one variable increases, the other does too. Conversely, -1 signifies a perfect negative correlation, where one variable increases as the other decreases. A value of 0 suggests no correlation.