QUAESTIONES GEOGRAPHICAE 30(2) • 2011 COMPARISON OF VALUES OF PEARSON’S AND SPEARMAN’S CORRELATION COEFFICIENTS ON THE SAME SETS OF DATA

abstract: Spearman’s rank correlation coefficient is a nonparametric (distribution-free) rank statistic proposed by Charles Spearman as a measure of the strength of an association between two variables. It is a measure of a monotone association that is used when the distribution of data makes Pearson’s correlation coefficient undesir-able or misleading. Spearman’s coefficient is not a measure of the linear relationship between two variables, as some “statisticians ” declare. It assesses how well an arbitrary monotonic function can describe a relationship between two variables, without making any assumptions about the frequency distribution of the variables. Un-like Pearson’s product-moment correlation coefficient, it does not require the assumption that the relationship between the variables is linear, nor does it require the variables to be measured on interval scales; it can be used for variables measured at the ordinal level. The idea of the paper is to compare the values of Pearson’s product-moment correlation coefficient and Spearman’s rank correlation coefficient as well as their statistical significance for different sets of data (original- for Pearson’s coefficient, and ranked data for Spearman’s coefficient) describ-ing regional indices of socio-economic development