Mean, Standard Deviation, Variance in Haskell

Stats.hs

module Main where

import Control.Applicative

{- Result = (Mean = 0.34, St. Dev = 0.115, Variance = 0.005) -}
main :: IO ()
main = interact stats
  where 
    length' = fromIntegral . length
    stats d = show (avg, stdDev, variance)
      where 
        results :: [Float]
	results = map read $ lines d
	avg, stdDev :: Float
	avg = (/) <$> sum <*> length' $ results 
	stdDev = sqrt $ summedElements / lengthX
 	  where 
            lengthX = length' results
            summedElements = sum (map (\x -> (x - avg) ^ 2) results)
            variance = stdDev ^ 2