mathematics Article A New Grey Approach for Using SWARA and PIPRECIA Methods in a Group Decision-Making Environment Dragiša Stanujki´ c 1 , Darjan Karabaševi´ c 2, * , Gabrijela Popovi´ c 2 , Predrag S. Stanimirovi´ c 3 , Muzafer Saraˇ cevi´ c 4 , Florentin Smarandache 5 , Vasilios N. Katsikis 6 and Alptekin Uluta¸ s 7, *   Citation: Stanujki´ c, D.; Karabaševi´ c, D.; Popovi´ c, G.; Stanimirovi´ c, P.S.; Saraˇ cevi´ c, M.; Smarandache, F.; Katsikis, V.N.; Uluta¸ s, A. A New Grey Approach for Using SWARA and PIPRECIA Methods in a Group Decision-Making Environment. Mathematics 2021, 9, 1554. https:// doi.org/10.3390/math9131554 Academic Editors: Svajon ˙ e Bekešien ˙ e and Ieva Meidut ˙ e-Kavaliauskien ˙ e Received: 31 May 2021 Accepted: 30 June 2021 Published: 1 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Technical Faculty in Bor, University of Belgrade, Vojske Jugoslavije 12, 19210 Bor, Serbia; dstanujkic@tfbor.bg.ac.rs 2 Faculty of Applied Management, Economics and Finance, University Business Academy in Novi Sad, Jevrejska 24, 11000 Belgrade, Serbia; gabrijela.popovic@mef.edu.rs 3 Faculty of Sciences and Mathematics, University of Niš, Višegradska 33, 18000 Niš, Serbia; pecko@pmf.ni.ac.rs 4 Department of Computer Sciences, University of Novi Pazar, Dimitrija Tucovi´ ca bb, 36300 Novi Pazar, Serbia; muzafers@uninp.edu.rs 5 Mathematics and Science Division, Gallup Campus, University of New Mexico, 705 Gurley Ave., Gallup, NM 87301, USA; smarand@unm.edu 6 Department of Economics, Division of Mathematics and Informatics, National and Kapodistrian University of Athens, Panepistimiopolis, 15784 Ilissia, Greece; vaskatsikis@econ.uoa.gr 7 Department of International Trade and Logistics, Faculty of Economics and Administrative Sciences, Sivas Cumhuriyet University, 58140 Sivas, Turkey * Correspondence: darjan.karabasevic@mef.edu.rs (D.K.); aulutas@cumhuriyet.edu.tr (A.U.) Abstract: The environment in which the decision-making process takes place is often characterized by uncertainty and vagueness and, because of that, sometimes it is very hard to express the criteria weights with crisp numbers. Therefore, the application of the Grey System Theory, i.e., grey numbers, in this case, is very convenient when it comes to determination of the criteria weights with partially known information. Besides, the criteria weights have a significant role in the multiple criteria decision-making process. Many ordinary multiple criteria decision-making methods are adapted for using grey numbers, and this is the case in this article as well. A new grey extension of the certain multiple criteria decision-making methods for the determination of the criteria weights is proposed. Therefore, the article aims to propose a new extension of the Step-wise Weight Assessment Ratio Analysis (SWARA) and PIvot Pairwise Relative Criteria Importance Assessment (PIPRECIA) methods adapted for group decision-making. In the proposed approach, attitudes of decision-makers are transformed into grey group attitudes, which allows taking advantage of the benefit that grey numbers provide over crisp numbers. The main advantage of the proposed approach in relation to the use of crisp numbers is the ability to conduct different analyses, i.e., considering different scenarios, such as pessimistic, optimistic, and so on. By varying the value of the whitening coefficient, different weights of the criteria can be obtained, and it should be emphasized that this approach gives the same weights as in the case of crisp numbers when the whitening coefficient has a value of 0.5. In addition, in this approach, the grey number was formed based on the median value of collected responses because it better maintains the deviation from the normal distribution of the collected responses. The application of the proposed approach was considered through two numerical illustrations, based on which appropriate conclusions were drawn. Keywords: grey numbers; group decision-making; PIPRECIA; SWARA 1. Introduction Multiple-Criteria Decision-Making (MCDM) aims to provide the decision-maker with a choice of the best options from the final set of alternatives by analyzing them from several angles, i.e., through several criteria/attributes. Criteria weights can have a significant impact on the ranking of alternatives or the selection of the most acceptable alternative Mathematics 2021, 9, 1554. https://doi.org/10.3390/math9131554 https://www.mdpi.com/journal/mathematics