Three age groups were formed randomly mixed. In the first one there were children from 14 to 24 months, in the second 25 to 35 months and in the third one from 36 to 48 months of age.
De manera arbitraria, se conformaron 3 grupos de edad de ambos sexos, en el primero se agruparon los infantes cuya edad se encontraba entre los 14 a 24 meses, en el segundo de 25 a 35 meses y en el tercero de 36 a 48 meses.