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lib/PhpSpreadsheet/Calculation/Statistical/Confidence.php

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+<?php
+
+namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical;
+
+use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception;
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
+
+class Confidence
+{
+    use ArrayEnabled;
+
+    /**
+     * CONFIDENCE.
+     *
+     * Returns the confidence interval for a population mean
+     *
+     * @param mixed $alpha As a float
+     *                      Or can be an array of values
+     * @param mixed $stdDev Standard Deviation as a float
+     *                      Or can be an array of values
+     * @param mixed $size As an integer
+     *                      Or can be an array of values
+     *
+     * @return array|float|string If an array of numbers is passed as an argument, then the returned result will also be an array
+     *            with the same dimensions
+     */
+    public static function CONFIDENCE(mixed $alpha, mixed $stdDev, mixed $size)
+    {
+        if (is_array($alpha) || is_array($stdDev) || is_array($size)) {
+            return self::evaluateArrayArguments([self::class, __FUNCTION__], $alpha, $stdDev, $size);
+        }
+
+        try {
+            $alpha = StatisticalValidations::validateFloat($alpha);
+            $stdDev = StatisticalValidations::validateFloat($stdDev);
+            $size = StatisticalValidations::validateInt($size);
+        } catch (Exception $e) {
+            return $e->getMessage();
+        }
+
+        if (($alpha <= 0) || ($alpha >= 1) || ($stdDev <= 0) || ($size < 1)) {
+            return ExcelError::NAN();
+        }
+        /** @var float $temp */
+        $temp = Distributions\StandardNormal::inverse(1 - $alpha / 2);
+
+        return Functions::scalar($temp * $stdDev / sqrt($size));
+    }
+}