Research Article Correlation Coefficient and Entropy Measures Based on Complex Dual Type-2 Hesitant Fuzzy Sets and Their Applications Tahir Mahmood , 1 Zeeshan Ali , 1 Harish Garg , 2 Lemnaouar Zedam , 3 and Ronnason Chinram 4,5 1 Department of Mathematics and Statistics, International Islamic University Islamabad, Islamabad, Pakistan 2 School of Mathematics, apar Institute of Engineering & Technology, Deemed University, Patiala 147004, Punjab, India 3 Laboratory of Pure and Applied Mathematics, Department of Mathematics, Med Boudiaf University of M’Sila, P.O. Box 166 Ichbilia, M’Sila 28000, Algeria 4 Algebra and Applications Research Unit, Division of Computational Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90110, ailand 5 Centre of Excellence in Mathematics, Si Ayuthaya Road, Bangkok 10400, ailand Correspondence should be addressed to Ronnason Chinram; ronnason.c@psu.ac.th Received 7 August 2020; Revised 19 October 2020; Accepted 21 October 2020; Published 8 March 2021 Academic Editor: Mehdi Ghatee Copyright © 2021 Tahir Mahmood et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e theory of complex dual type-2 hesitant fuzzy sets (CDT-2HFSs) is a blend of two different modifications of fuzzy sets (FSs), called complex fuzzy sets (CFSs) and dual type-2 hesitant fuzzy sets (DT-2HFSs). CDT-2HFS is a proficient technique to cope with unpredictable and awkward information in realistic decision problems. CDT-2HFS is composed of the grade of truth and the grade of falsity, and the grade of truth (also for grade of falsity) contains the grade of primary and secondary parts in the form of polar coordinates with the condition that the sum of the maximum of the real part (also for the imaginary part) of the primary grade (also for the secondary grade) cannot exceed the unit interval [0, 1]. e aims of this manuscript are to discover the novel approach of CDT-2HFS and its operational laws. ese operational laws are also justified with the help of an example. Ad- ditionally, based on a novel CDT-2HFS, we explored the correlation coefficient (CC) and entropy measures (EMs), and their special cases are also discussed. TOPSIS method based on CDT-2HFS is also explored. en, we applied our explored measures based on CDT-2HFSs in the environment of the TOPSIS method, medical diagnosis, pattern recognition, and clustering al- gorithm to cope with the awkward and complicated information in realistic decision issues. Finally, some numerical examples are given to examine the proficiency and validity of the explored measures. Comparative analysis, advantages, and graphical in- terpretation of the explored measures with some other existing measures are also discussed. 1. Introduction e present decision-making is one of the genuinely basic movements in individuals’ everyday life, the reason for existing of which is to rank the limited arrangement of options regarding that they are so solid to the choice maker(s). Multiattribute decision-making (MADM) is a part of decision-making and is viewed as an intellectual-based human movement. People unavoidably are confronted with different decision-making issues, which include numerous fields [1–3]. e idea of the fuzzy set (FS) proposed by Zadeh [4] modified the method of measuring the vulnerability/ fuzziness. Before the development of the FS hypothesis by Zadeh [4], the likelihood hypothesis was the customary instrument to quantify the vulnerability. Be that as it may, to gauge the vulnerability utilizing likelihood, it ought to have been communicated as exact numbers which are its primary constraints. e obscure terms, for instance, “without doubt” and “marginally,” could not be measured utilizing the likelihood hypothesis. To gauge the Hindawi Journal of Mathematics Volume 2021, Article ID 2568391, 34 pages https://doi.org/10.1155/2021/2568391