# File lib/benelux/stats.rb, line 221
221:       def sd
222:         return 0.0 if @n <= 1
223:         # (sqrt( ((s).sumsq - ( (s).sum * (s).sum / (s).n)) / ((s).n-1) ))
224:         begin
225:           return Math.sqrt( (@sumsq - (@sum * @sum / @n)) / (@n-1) )
226:         rescue Errno::EDOM
227:           return 0.0
228:         end
229:       end