simpangan baku data 5,5,5,4,6,7,7,9 adalah?

Nilai rata-rata :
5,5,5,4,6,7,7,9 = 4+5+5+5+6+7+7+9
                        = 48/8
                        = 6

Ragam :
s²= (1/6)*((4-6)²+(5-6)²+(5-6)²+(5-6)²+(6-6)²+(7-6)²+(7-6)²+(9-6)²)
   = 1/6*(4+1+1+1+0+1+1+9)
   = 1/6*(18)
   = 18/6
   = 3

Simpangan baku :
s = √s²
s = √3