Which of the following is not a measure of correlation?

The correct answer is identified because "Value range" does not serve as a measure of correlation. Instead, it refers to the broad concept of the span between the minimum and maximum values in a dataset, providing insight into the extent of data variation but not its relationship or association between two variables.

In contrast, Pearson's r, Spearman's rho, and Kendall's tau are all established measures of correlation that specifically assess the strength and direction of the relationship between pairs of numerical or ordinal data. Pearson's r measures linear correlation, indicating how closely two variables converge along a straight line. Spearman's rho evaluates the strength and direction of the association between ranked variables, while Kendall's tau, like Spearman's, is concerned with the ordinal ranking of data but focuses on concordant and discordant pairs to derive its metric.

Thus, while the first three options provide meaningful insights into the correlation between variables, the value range does not offer a measure of that relationship.