sd1 and sd2 are the standard deviation of two array .
$ sd1 = sd ( $ arr1 , $ n ) ; $ sd2 = sd ( $ arr2 , $ m ) ; echo ( " StandardDeviation1 : " ▁ . ▁ round ( $ sd1 , ▁ 2 ) ▁ . ▁ " " STRNEWLINE . ▁ " StandardDeviation2 : "