A new correlation measure of the intuitionistic fuzzy sets

In this paper, we regard the membership degree and the non-membership degree of the intuitionistic fuzzy set (IFS) as a whole and propose a new approach to measuring the correlation degree between the IFSs in finite sets. Like the computational process of the correlation coefficient between the real number variables, we first define the deviation of the intuitionistic fuzzy numbers, the variance of the IFS, and the covariance of the IFSs; then propose the formula to get the correlation coefficient between the IFSs. The proposed method not only reflects the symbol attribute of the correlation degree between the IFSs (the value of the correlation coefficient lies in the interval [-1, 1]), but also makes sure the integrity of the IFS is maintained. Several examples are given to show the feasibility and advantages of the proposed method. Moreover, we extend this approach to the interval-valued intuitionistic fuzzy set (IVIFS) case.