public function getStandardDeviation($Serie)
    {
        if (isset($this->Data["Series"][$Serie])) {
            $Average = $this->getSerieAverage($Serie);
            $SerieData = $this->stripVOID($this->Data["Series"][$Serie]["Data"]);

            $DeviationSum = 0;
            foreach ($SerieData as $Key => $Value) {
                $DeviationSum = $DeviationSum + ($Value - $Average) * ($Value - $Average);
            }
            return sqrt($DeviationSum / count($SerieData));
        }
        return null;
    }