return the standard deviation of a dice roll from the dice d (floating point value). Dice have the format xdy where x is the number of times to roll and y is the number of sides on the dice. An optional +n or -n may be appended to the dice.
Displays 2.04. This means that 66% of the time, the dice roll will be within the average (9) plus or minus 2.04. Or, roughly 66% of the time the result will be between 7 and 11 inclusive.
%abs