Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Statistical.php
public static function ZTEST($dataSet, $m0, $sigma = null)
    {
        $dataSet = Functions::flattenArrayIndexed($dataSet);
        $m0 = Functions::flattenSingleValue($m0);
        $sigma = Functions::flattenSingleValue($sigma);

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

        return 1 - self::NORMSDIST((self::AVERAGE($dataSet) - $m0) / ($sigma / sqrt($n)));
    }
public static function ZTEST($dataSet, $m0, $sigma = null)
    {
        $dataSet = Functions::flattenArrayIndexed($dataSet);
        $m0 = Functions::flattenSingleValue($m0);
        $sigma = Functions::flattenSingleValue($sigma);

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

        return 1 - self::NORMSDIST((self::AVERAGE($dataSet) - $m0) / ($sigma / sqrt($n)));
    }
ZTEST.

Returns the Weibull distribution. Use this distribution in reliability
analysis, such as calculating a device's mean time to failure.

@param float $dataSet
@param float $m0 Alpha Parameter
@param float $sigma Beta Parameter

@return float