lispdoc  results for standarddeviation 
(alexandria.0.dev:standarddeviation sample &key (biased t))  Function: Standard deviation of SAMPLE. Returns the biased standard deviation if BIASED is true (the default), and the square root of the unbiased estimator for variance if BIASED is false (which is not the same as the unbiased estimator for standard deviation). SAMPLE must be a sequence of numbers.

By Bill Moorier 