Calcolo varianza
CALCOLO VARIANZA PRIMARIA
https://docs.google.com/forms/d/1fSjaRilm4CvIzQj-bDC18jNwQcV-2W1jpscYBtAlH5o/edit?usp=sharing
CALCOLO VARIANZA SECONDARIA
https://docs.google.com/forms/d/11IvqmakA4ZgB9FZk3tKIVu_cD6CBYIqs33EjT674D9k/edit?usp=sharing