module Enumerable

# File lib/enumerable.rb, line 3
def mean
  self.reduce(:+) / self.length.to_f
end

# File lib/enumerable.rb, line 12
def standard_deviation
  Math.sqrt(self.variance)
end

# File lib/enumerable.rb, line 7
def variance
  mean = self.mean
  self.reduce(0) { |memo, value| memo + ((value - mean) ** 2) } / (self.length - 1).to_f
end