Spearman rank correlation coefficient

The Spearman rank correlation coefficient is a statistical measure used to quantify the relationship between two variables when the data is in the form of rank orders. It assesses the strength of a monotonic association, meaning the variables tend to change in the same or opposite direction consistently.12

For example, it could be used to determine the level of agreement between two individuals ranking a list of items. A coefficient of 1 indicates complete agreement, -1 signifies complete disagreement, and 0 suggests no relationship between the rankings. This method is particularly useful when data is ordinal or when interval data is converted to ranks, though this conversion can lead to a loss of information.12