enum.cr

module Enumerable
    def sum
      self.reduce(0){|accum, i| accum + i }
    end

    def mean
      self.sum/self.size.to_f
    end

    def variance
      m = self.mean
      sum = self.reduce(0){|accum, i| accum + (i-m)**2 }
      sum/(self.size - 1).to_f
    end

    def stddev
      return Math.sqrt(self.variance)
    end

end