The Spearman rank correlation coefficient between intuitionistic fuzzy sets

This paper is a continuation of our previous work on Pearson's coefficient r and we introduce the concept of the Spearman correlation coefficient between Atanassov's intuitionistic fuzzy sets (A-IFSs, for short) to measure the degree of association between A-IFSs when the assumption that the data distributions are normal is not valid or when data are in the form of ranks.