A Potions instructor at Hogwarts wishes to know the average age (in month) of his 200 students. He decides to choose 25 students from the class and ask them for their age. All 200 names are put in a sorting hat and 25 names are then chosen at random (without replacement). The average age of the students chosen is observed to be 231 months. The group of 25 students is known as what? The population size A census The population The sample The sample size.