simpangan baku dari data 90,70,80,40 adalah

X| = (90+70+80+40)/4
X| = 280/4 = 70

Sb² = [(90-70)²+(70-70)²+(80-70)²+(70-40)²]/4
Sb² = (400+0+100+900)/4
Sb² = (1400/4)
Sb² = 350
Sb = √350
sb = √(7×5×2×5)
Sb = 5√14
Sb = 18,70829