simpangan baku dari data 31, 35, 37, 38, 39 adalah

Cari rata rata terlebih dahulu.
x = ( 31+35+37+38+39 ) / 5
= 180 / 5
= 36

Masukkan rumus
(x-xi)²
(31-36)² = (-5)² = 25
(35-36)² = (-1)² = 1
(37-36)² = (1)² = 1
(38-36)² = (2)² = 4
(39-36)² = (3)² = 9
Total semua = 25+1+1+4+9
= 40

Jadi, simpangan baku
√40/√5 = √8 = 2√2