This investigation arises from evaluating the performances in Pruebas SABER census tests of students of the ninth grade in the area of mathematics, of the Educational Institutions Juan de La Cruz Posada and Héctor Abad Gómez of Medellín, Colombia; where 88 percent of the students in the sample were at the performance level of insufficient. The difficulty is accentuated in the random component regarding the use of the Arithmetic Mean to analyze the behavior of a data set. When the causes of these results were investigated, direct incidence of teaching practices was found; who teach the mathematical object in a traditional and decontextualized way; which implies that it does not acquire meaning inside and outside the school environment, remaining in a formula that the student forgets. The problem was addressed from the Resignification of the Arithmetic Mean under the Socio-epistemological theory. Which gives us a different perspective under the premise of focusing on the practices that give rise to the concept and not the same object itself, thus investigating the processes of production, acquisition and dissemination of new knowledge, which takes us away from the discourse traditional mathematician