The sample consisted of a selection of 8 groups of the morning shift 2 students per semester and 4 groups of the evening shift. This was due to the fact there were more groups in the morning shift than in the evening one.
La muestra se conformó seleccionando ocho grupos del turno matutino 2 por cada semestre estudiado y cuatro del turno vespertino, debido a que son más grupos en el turno matutino que en el vespertino.