question: public double kurtosis ( ) { double mu = mean ( ) ; double devsum = 0 ; double wsum = 0 ; int size = values . size ( ) ; for ( int i = 0 ; i < size ; i ++ ) { double dev = values . get ( i ) - mu ; devsum += Math . pow ( dev , 4.0d ) * weights . get ( i ) ; wsum += weights . get ( i ) ; } double mu4 = devsum / wsum ; double s4 = Math . pow ( variance ( ) , 4.0 / 2.0 ) ; return mu4 / s4 ; }
target:  Returns the (weighted) kurtosis (not excess kurtosis) of all samples.