Correlation analysis of sequences with interval grey numbers based on the kernel and greyness degree

Purpose - The purpose of this paper is to propose an extending correlation analysis method to deal with the correlation analysis between the sequences with incomplete information. Design/methodology/approach - Based on the axiomatic definition of a grey number and its greyness degree in grey system theory, the whitenization mean, whitenization difference, whitenization covariance of sequences with interval grey numbers and their greyness degrees are defined in turn. In addition, the whitenization correlation coefficient and its greyness degree of sequences with interval grey numbers are also defined. By using the relationship between the greyness degree and kernel for a grey number, the transformation formula from the whitenization value and greyness degree of correlation coefficient to form of interval grey numbers are put forward further. Findings - The whitenization value of correlation coefficient efficient of two arbitrary sequences with interval grey numbers have symmetry, with same greyness degree but without normalization in the interval [-, 1]; the mean, difference, covariance and correlation coefficient defined in statistics are all the special cases of those in sequences with interval grey numbers. Research limitations/implications - Due to the complexity of operation of grey numbers, the reliability of correlation coefficient of interval numbers sequence is difficult to be tested by constructing statistics at present. The further research is needed. Practical implications The correlation analysis method of interval grey numbers can contribute to the further researches on the incomplete information system in the real world. Originality/value - On the basis of grey system theory, a correlation analysis method for analyzing information incomplete sequences is proposed.