“…Since the teacher might be able to change the mean for a better level or not, a teaching factor (T F ) is assigned that can be either 1 or 2, and r i is a number between [0,1] that randomly decides what the mean value is. Hence, the new level of each student (X new,i ) can be improved according to the mean difference using (19)(20)(21) [26], and if the new level of a student gives better function value, it is accepted for proceeding the optimization.…”