Graduate T.E.I. of Western Greece Professor Emeritus of Mathematical Sciences School of Technological Applications


The methods of assessing the individuals’ performance usually applied in practice are based on principles of the bivalent logic (yes-no). However, fuzzy logic, due to its nature of including multiple values, offers a wider and richer field of resources for this purpose. In this paper we use principles of fuzzy logic in developing a new method for assessing the performance of groups of individuals participating in any human activity. For this, we represent each of the groups under assessment as a fuzzy subset of a set of linguistic labels characterizing their members’ performance and we use the centre of gravity defuzzification technique in converting the fuzzy data collected from the corresponding activity to a crisp number. The resulting structure provides a weighted assessment, in which the higher is an individual’s performance the more its “contribution” to the corresponding group’s performance. Thus, in contrast to the mean of the scores (i.e. numerical values of the performance) of all the group’s members, which is connected to the mean group’s performance, our method is connected somehow to the group’s quality performance. Two real applications are also presented, related to the bridge players’ performance and the students’ problem solving skills respectively, illustrating the importance of our assessment method in practice.