samples in weights 12, 6, 7, 3 and 10?

Question

compute the range
compute the mean deviation
compute the standard deviation

Answer 1

The range is the largest minus the smallest, or 12-3
mean & std dev.:
x, f, r,rf, fr^2
3, 1, -4, -4, 16
4, , -3, ,
5, , -2, ,
6, 1, -1, -1, 1
7, 1, 0, 0, 0
8, , 1, ,
9, , 2, ,
10, 1, 3, +3, 9
11 , , 4, ,
12, 1, 5, +5, 25
sums,,,,,,,,3, 53
m = 7+3/5 = 7.6
σ ≈ √(53/5) ≈ 3.2558
Technically,
σ = √((4.4² + 1.6² + 0.6² + 4.6² + 2.4²/5)
σ = 3.1369