find the mean deviation of 1, 2, 3 and 4

Explanation

X = 1, 2, 3, 4; ∑X = 10
x = ∑X/n = 10/4 = 2.5
X - x = -1.5, -0.5, 0.5, 1.5
lX - xl = 1.5, 0.5, 0.5, 1.5; ∑lX - xl = 4.0
mean deviation = (∑lX - xl)/n
= 4.0/4
= 1.0