question: public void calculateDerived ( ) { mean = Double . NaN ; stdDev = Double . NaN ; if ( count > 0 ) { mean = sum / count ; stdDev = Double . POSITIVE_INFINITY ; if ( count > 1 ) { stdDev = sumSq - ( sum * sum ) / count ; stdDev /= ( count - 1 ) ; if ( stdDev < 0 ) { stdDev = 0 ; } stdDev = Math . sqrt ( stdDev ) ; } } }
target:  Tells the object to calculate any statistics that don't have their values automatically updated during add. Currently updates the mean and standard deviation.