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<?php $aValues = array(9,4,-3,-10); function standard_deviation($aValues, $bSample = false) { $fMean = array_sum($aValues) / count($aValues); $fVariance = 0.0; foreach ($aValues as $i) { $fVariance += pow($i - $fMean, 2); } $fVariance /= ( $bSample ? count($aValues) - 1 : count($aValues) ); return (float) sqrt($fVariance); } ?>

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