Question

Prove that sum of deviation is zero for 121 122 123 124 125 126 127 128 129 130

Answer 1

mean = (121+122+123+124+125+126+127+128+129+130) / 10
= 1255 / 10
= 125.5

Deviations,
a1 = 121 - 125.5 = -4.5
a2 = 122 - 125.5 = -3.5
a3 = 123 - 125.5 = -2.5
a4 = 124 - 125.5 = -1.5
a5 = 125 - 125.5 = -0.5
a6 = 126 - 125.5 = 0.5
a7 = 127 - 125.5 = 1.5
a8 = 128 - 125.5 = 2.5
a9 = 129 - 125.5 = 3.5
a10 = 130 - 125.5 = 4.5

Sum of dviations = a1+a2+a3+.....+a10
= -4.5 - 3.5 - 2.5 - 1.5 - 0.5 +0.5 + 1.5 + 2.5 + 3.5 + 4.5
= 0