stats.hs

import Data.List (genericLength)                                                                 
                                                                                                 
mean xs = sum xs / genericLength  xs                                                             
                                                                                                 
variance xs = (sum [ (x - m)^2 | x <- xs ]) / genericLength xs                                   
  where m = mean xs                                                                              
                                                                                                 
standardDeviation xs = sqrt $ variance xs