Calculating a z score

[@user-pw8bn6hy1f]

Why (M = 3) ?

[@charlesvanliew9927]

The mean is obtained by adding the scores and dividing by the number of scores. Here, the sum of the scores is 1 + 2 + 3 + 4 + 5 = 15. 15 divided by 5 (the number of scores) is 3. So, M = 3.