The Mean = (135 + 71 + 69 + 80 + 158 + 152 + 161 + 96 + 122 + 118 + 87 + 85 ) : 12 = 111.166
The smallest value : 69
The greatest value : 161
s² = ∑( x i - x )² / ( n - 1 )
s² = ( 568.274 + 1613.3 + 1777.97 + 971.32 + 2193.42 + 1667.4 + +2483.42 + 230 + 117.38 + 46.7 + 584 + 684.66 ) : 11
s² = 1176.1676
s = √s² = √1176.1676
s ( Standard deviation ) = 34.295
All the values fall within 2 standard deviations:
x (Mean) - 2 s and x + 2 s