math.statistics: fix typo
math.statistics: fix typo

mrjbq7/factor,mrjbq7/factor,factor/factor,mrjbq7/factor,factor/factor,tgunr/factor,mrjbq7/factor,tgunr/factor,factor/factor,tgunr/factor,tgunr/factor,mrjbq7/factor,factor/factor,mrjbq7/factor,tgunr/factor,factor/factor,factor/factor,tgunr/factor