x1 = 40;
x2 = 43;
x3 = 39;
x4 = 35;
avg = (x1 + x2 + x3 + x4) / 4;
variance = ((x1 - avg) ^ 2 + (x2 - avg) ^ 2 + (x3 - avg) ^ 2 + (x4 - avg) ^ 2) / 3
var([x1 x2 x3 x4])
