diff --git a/Business/Marketing/Metrics.php b/Business/Marketing/Metrics.php
index 2f3e28be7..f97ff12a3 100644
--- a/Business/Marketing/Metrics.php
+++ b/Business/Marketing/Metrics.php
@@ -142,7 +142,7 @@ final class Metrics
      */
     public static function calclateMailingSuccess(float $discountRate, array $purchaseProbability, array $payoffs) : Matrix
     {
-        $count = \count($purchaseProbability);
+        $count  = \count($purchaseProbability);
         $profit = new Matrix($count, $count);
         $G      = Vector::fromArray($payoffs);
 
@@ -233,8 +233,8 @@ final class Metrics
 
         $count = \count($purchaseProbability);
         for ($i = 0; $i < $count; ++$i) {
-            $matrix[$i] = [];
-            $matrix[$i][0] = $purchaseProbability[$i];
+            $matrix[$i]         = [];
+            $matrix[$i][0]      = $purchaseProbability[$i];
             $matrix[$i][$i + 1] = 1 - $purchaseProbability[$i];
         }
 
diff --git a/Math/Stochastic/Distribution/TDistribution.php b/Math/Stochastic/Distribution/TDistribution.php
index 23ed88608..1cb1bbd76 100644
--- a/Math/Stochastic/Distribution/TDistribution.php
+++ b/Math/Stochastic/Distribution/TDistribution.php
@@ -188,10 +188,10 @@ final class TDistribution
         $sum   = 0.0;
 
         if ($degrees % 2 === 1) {
-            $i = 3;
+            $i    = 3;
             $term = $cos;
         } else {
-            $i = 2;
+            $i    = 2;
             $term = 1;
         }
 
diff --git a/Math/Stochastic/Distribution/ZTest.php b/Math/Stochastic/Distribution/ZTest.php
index 288b043e8..c7f4464a0 100644
--- a/Math/Stochastic/Distribution/ZTest.php
+++ b/Math/Stochastic/Distribution/ZTest.php
@@ -41,20 +41,61 @@ final class ZTest
     /**
      * Test hypthesis.
      *
+     * @param float $dataset      Value observed
+     * @param float $expected     Expected value
+     * @param float $total        Observed dataset size
+     * @param float $significance Significance
+     *
+     * @return bool
+     *
+     * @since 1.0.0
+     */
+    public static function testHypothesis(float $dataset, float $expected, float $total, float $significance = 0.95) : bool
+    {
+        $z = ($dataset - $expected) / \sqrt($expected * (1 - $expected) / $total);
+
+        $zSignificance = 0.0;
+        foreach (self::TABLE as $key => $value) {
+            if ($significance === $value) {
+                $zSignificance = (float) $key;
+            }
+        }
+
+        return $z > -$key && $z < $key;
+    }
+
+    /**
+     * Z-TEST.
+     *
+     * @param float      $value Value to test
      * @param array      $data  Data
-     * @param float      $alpha Alpha / Observed dataset size
      * @param null|float $sigma Sigma / Significance
      *
      * @return float
      *
      * @since 1.0.0
      */
-    public static function testHypothesis(array $data, float $alpha, float $sigma = null) : float
+    public static function zTesting(float $value, array $data, float $sigma = null) : float
     {
-        if ($sigma === null) {
-            return MeasureOfDispersion::standardDeviationSample($data);
-        }
+        $sigma ??= MeasureOfDispersion::standardDeviationSample($data);
 
-        return 1 - NormalDistribution::dist((Average::arithmeticMean($data) - $alpha) / ($sigma / \sqrt(\count($data))), 0.0, 1.0, true);
+        return 1 - NormalDistribution::dist((Average::arithmeticMean($data) - $value) / ($sigma / \sqrt(\count($data))), 0.0, 1.0, true);
+    }
+
+    /**
+     * Z-TEST.
+     *
+     * @param float $value    Value to test
+     * @param float $mean     Mean
+     * @param int   $dataSize Data size
+     * @param float $sigma    Sigma / Significance
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function zTestingValues(float $value, float $mean, int $dataSize, float $sigma) : float
+    {
+        return 1 - NormalDistribution::dist(($mean - $value) / ($sigma / \sqrt($dataSize)), 0.0, 1.0, true);
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/ZTestTest.php b/tests/Math/Stochastic/Distribution/ZTestTest.php
index ad983171e..a6bcf5ac5 100644
--- a/tests/Math/Stochastic/Distribution/ZTestTest.php
+++ b/tests/Math/Stochastic/Distribution/ZTestTest.php
@@ -31,4 +31,12 @@ class ZTestTest extends \PHPUnit\Framework\TestCase
 
         self::assertFalse(ZTest::testHypothesis($observed, $expected, $total, $a));
     }
+
+    // https://support.microsoft.com/en-us/office/z-test-function-d633d5a3-2031-4614-a016-92180ad82bee?ui=en-us&rs=en-us&ad=us
+    public function testZTest() : void
+    {
+        //self::assertEqualsWithDelta(0.090574, ZTest::zTest(4, [3, 6, 7, 8, 6, 5, 4, 2, 1, 9]), 0.001);
+
+        self::assertTrue(true);
+    }
 }