StandardNormal.php

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<?php

namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;

use PhpOffice\PhpSpreadsheet\Calculation\Functions;
use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Averages;
use PhpOffice\PhpSpreadsheet\Calculation\Statistical\StandardDeviations;

class StandardNormal
{
    public static function cumulative($value)
    {
        return Normal::distribution($value, 0, 1, true);
    }

    public static function distribution($value, $cumulative)
    {
        return Normal::distribution($value, 0, 1, $cumulative);
    }

    public static function inverse($value)
    {
        return Normal::inverse($value, 0, 1);
    }

    public static function gauss($value)
    {
        $value = Functions::flattenSingleValue($value);
        if (!is_numeric($value)) {
            return Functions::VALUE();
        }

        return self::distribution($value, true) - 0.5;
    }

    public static function zTest($dataSet, $m0, $sigma = null)
    {
        $dataSet = Functions::flattenArrayIndexed($dataSet);
        $m0 = Functions::flattenSingleValue($m0);
        $sigma = Functions::flattenSingleValue($sigma);

        if (!is_numeric($m0) || ($sigma !== null && !is_numeric($sigma))) {
            return Functions::VALUE();
        }

        if ($sigma === null) {
            $sigma = StandardDeviations::STDEV($dataSet);
        }
        $n = count($dataSet);

        return 1 - self::cumulative((Averages::average($dataSet) - $m0) / ($sigma / sqrt($n)));
    }
}