diff --git a/Config/SettingsAbstract.php b/Config/SettingsAbstract.php
index d05f7da53..745ead076 100644
--- a/Config/SettingsAbstract.php
+++ b/Config/SettingsAbstract.php
@@ -14,7 +14,6 @@ declare(strict_types=1);
 
 namespace phpOMS\Config;
 
-use phpOMS\DataStorage\Database\DatabaseExceptionFactory;
 use phpOMS\DataStorage\Database\Query\Builder;
 use phpOMS\DataStorage\Cache\CachePool;
 use phpOMS\DataStorage\Database\Connection\ConnectionAbstract;
@@ -117,10 +116,7 @@ abstract class SettingsAbstract implements OptionsInterface
             return \count($options) > 1 ? $options : \reset($options);
         } catch (\PDOException $e) {
             // @codeCoverageIgnoreStart
-            $exception = DatabaseExceptionFactory::createException($e);
-            $message   = DatabaseExceptionFactory::createExceptionMessage($e);
-
-            throw new $exception($message);
+            echo $e->getMessage();
             // @codeCoverageIgnoreEnd
         }
     }
diff --git a/DataStorage/Database/DatabaseExceptionFactory.php b/DataStorage/Database/DatabaseExceptionFactory.php
deleted file mode 100644
index 64ffaf630..000000000
--- a/DataStorage/Database/DatabaseExceptionFactory.php
+++ /dev/null
@@ -1,66 +0,0 @@
-<?php
-/**
- * Orange Management
- *
- * PHP Version 7.4
- *
- * @package   phpOMS\DataStorage\Database
- * @copyright Dennis Eichhorn
- * @license   OMS License 1.0
- * @version   1.0.0
- * @link      https://orange-management.org
- */
-declare(strict_types=1);
-
-namespace phpOMS\DataStorage\Database;
-
-use phpOMS\DataStorage\Database\Schema\Exception\TableException;
-
-/**
- * Database exception factory.
- *
- * @package phpOMS\DataStorage\Database
- * @license OMS License 1.0
- * @link    https://orange-management.org
- * @since   1.0.0
- */
-class DatabaseExceptionFactory
-{
-    /**
-     * Create exception class string based on exception.
-     *
-     * @param \PDOException $e Exception
-     *
-     * @return string Returns exception namespace/class
-     *
-     * @since 1.0.0
-     */
-    public static function createException(\PDOException $e) : string
-    {
-        switch ($e->getCode()) {
-            case '42S02':
-                return '\phpOMS\DataStorage\Database\Schema\Exception\TableException';
-            default:
-                return '\PDOException';
-        }
-    }
-
-    /**
-     * Create exception message based on exception.
-     *
-     * @param \PDOException $e Exception
-     *
-     * @return string Returns exception pessage
-     *
-     * @since 1.0.0
-     */
-    public static function createExceptionMessage(\PDOException $e) : string
-    {
-        switch ($e->getCode()) {
-            case '42S02':
-                return TableException::findTable($e->getMessage());
-            default:
-                return $e->getMessage();
-        }
-    }
-}
diff --git a/DataStorage/Database/Schema/Exception/TableException.php b/DataStorage/Database/Schema/Exception/TableException.php
deleted file mode 100644
index ed93b218f..000000000
--- a/DataStorage/Database/Schema/Exception/TableException.php
+++ /dev/null
@@ -1,68 +0,0 @@
-<?php
-/**
- * Orange Management
- *
- * PHP Version 7.4
- *
- * @package   phpOMS\DataStorage\Database\Schema\Exception
- * @copyright Dennis Eichhorn
- * @license   OMS License 1.0
- * @version   1.0.0
- * @link      https://orange-management.org
- */
-declare(strict_types=1);
-
-namespace phpOMS\DataStorage\Database\Schema\Exception;
-
-/**
- * Path exception class.
- *
- * @package phpOMS\DataStorage\Database\Schema\Exception
- * @license OMS License 1.0
- * @link    https://orange-management.org
- * @since   1.0.0
- */
-class TableException extends \PDOException
-{
-    /**
-     * Constructor.
-     *
-     * @param string     $message  Exception message
-     * @param int        $code     Exception code
-     * @param \Exception $previous Previous exception
-     *
-     * @since 1.0.0
-     */
-    public function __construct(string $message, int $code = 0, \Exception $previous = null)
-    {
-        parent::__construct('The table "' . $message . '" doesn\'t exist.', $code, $previous);
-    }
-
-    /**
-     * Get table name from exception.
-     *
-     * @param string $message Exception message
-     *
-     * @return string
-     *
-     * @since 1.0.0
-     */
-    public static function findTable(string $message) : string
-    {
-        $pos1 = \strpos($message, '\'');
-
-        if ($pos1 === false) {
-            return $message;
-        }
-
-        $pos2 = \strpos($message, '\'', $pos1 + 1);
-
-        if ($pos2 === false) {
-            return $message;
-        }
-
-        $table = \substr($message, $pos1 + 1, $pos2 - $pos1 - 1);
-
-        return $table === false ? $message : $table;
-    }
-}
diff --git a/Math/Stochastic/Distribution/BernoulliDistribution.php b/Math/Stochastic/Distribution/BernoulliDistribution.php
index be8a7f3b2..b641b5618 100644
--- a/Math/Stochastic/Distribution/BernoulliDistribution.php
+++ b/Math/Stochastic/Distribution/BernoulliDistribution.php
@@ -136,6 +136,20 @@ class BernoulliDistribution
         return $p * (1 - $p);
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $p Value p
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $p) : float
+    {
+        return \sqrt(self::getVariance($p));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/BetaDistribution.php b/Math/Stochastic/Distribution/BetaDistribution.php
index 7eded53f2..3baa94fd4 100644
--- a/Math/Stochastic/Distribution/BetaDistribution.php
+++ b/Math/Stochastic/Distribution/BetaDistribution.php
@@ -78,6 +78,21 @@ class BetaDistribution
         return $alpha * $beta / (($alpha + $beta) ** 2 * ($alpha + $beta + 1));
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $alpha Alpha
+     * @param float $beta  Beta
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $alpha, float $beta) : float
+    {
+        return \sqrt(self::getVariance($alpha, $beta));
+    }
+
     /**
      * Get skewness.
      *
@@ -123,7 +138,7 @@ class BetaDistribution
     public static function getMgf(float $t, float $alpha, float $beta) : float
     {
         $sum = 0;
-        for ($k = 1; $k < 100000; ++$k) {
+        for ($k = 1; $k < 20; ++$k) {
             $product = 1;
             for ($r = 0; $r < $k - 1; ++$r) {
                 $product *= ($alpha + $r) / ($alpha + $beta + $r);
diff --git a/Math/Stochastic/Distribution/BinomialDistribution.php b/Math/Stochastic/Distribution/BinomialDistribution.php
index 101d8cd28..c79c513a3 100644
--- a/Math/Stochastic/Distribution/BinomialDistribution.php
+++ b/Math/Stochastic/Distribution/BinomialDistribution.php
@@ -187,4 +187,19 @@ class BinomialDistribution
     {
         return $n * $p * (1 - $p);
     }
+
+    /**
+     * Get standard deviation.
+     *
+     * @param int   $n Value n
+     * @param float $p Value p
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(int $n, float $p) : float
+    {
+        return \sqrt(self::getVariance($n, $p));
+    }
 }
diff --git a/Math/Stochastic/Distribution/ChiSquaredDistribution.php b/Math/Stochastic/Distribution/ChiSquaredDistribution.php
index 64f69e0cf..d48036b3c 100644
--- a/Math/Stochastic/Distribution/ChiSquaredDistribution.php
+++ b/Math/Stochastic/Distribution/ChiSquaredDistribution.php
@@ -219,6 +219,20 @@ class ChiSquaredDistribution
         return 2 * $df;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param int $df Degrees of freedom
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(int $df) : float
+    {
+        return \sqrt(self::getVariance($df));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/ExponentialDistribution.php b/Math/Stochastic/Distribution/ExponentialDistribution.php
index 8148cf6f2..0aafa6554 100644
--- a/Math/Stochastic/Distribution/ExponentialDistribution.php
+++ b/Math/Stochastic/Distribution/ExponentialDistribution.php
@@ -108,6 +108,20 @@ class ExponentialDistribution
         return \pow($lambda, -2);
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $lambda Lambda
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $lambda) : float
+    {
+        return \sqrt(self::getVariance($lambda));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/FDistribution.php b/Math/Stochastic/Distribution/FDistribution.php
index 0232be259..f58a3a97b 100644
--- a/Math/Stochastic/Distribution/FDistribution.php
+++ b/Math/Stochastic/Distribution/FDistribution.php
@@ -76,6 +76,21 @@ class FDistribution
             / ($d1 * ($d2 - 2) ** 2 * ($d2 - 4));
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param int $d1 Degree of freedom
+     * @param int $d2 Degree of freedom
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(int $d1, int $d2) : float
+    {
+        return \sqrt(self::getVariance($d1, $d2));
+    }
+
     /**
      * Get skewness.
      *
diff --git a/Math/Stochastic/Distribution/GammaDistribution.php b/Math/Stochastic/Distribution/GammaDistribution.php
index 5f84455fe..a54cd971a 100644
--- a/Math/Stochastic/Distribution/GammaDistribution.php
+++ b/Math/Stochastic/Distribution/GammaDistribution.php
@@ -160,6 +160,21 @@ class GammaDistribution
         return $k * $theta ** 2;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $k     k shape
+     * @param float $theta Theta scale
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviationK(float $k, float $theta) : float
+    {
+        return \sqrt(self::getVarianceK($k, $theta));
+    }
+
     /**
      * Get variance.
      *
@@ -175,6 +190,21 @@ class GammaDistribution
         return $alpha / ($beta ** 2);
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $alpha Alpha shape
+     * @param float $beta  Beta scale
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviationAlphaBeta(float $alpha, float $beta) : float
+    {
+        return \sqrt(self::getVarianceAlphaBeta($alpha, $beta));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/GeometricDistribution.php b/Math/Stochastic/Distribution/GeometricDistribution.php
index 2f3a72446..0d182a694 100644
--- a/Math/Stochastic/Distribution/GeometricDistribution.php
+++ b/Math/Stochastic/Distribution/GeometricDistribution.php
@@ -108,6 +108,20 @@ class GeometricDistribution
         return (1 - $p) / $p ** 2;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $p Value p
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $p) : float
+    {
+        return \sqrt(self::getVariance($p));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/HypergeometricDistribution.php b/Math/Stochastic/Distribution/HypergeometricDistribution.php
index 70abc2832..2895422fb 100644
--- a/Math/Stochastic/Distribution/HypergeometricDistribution.php
+++ b/Math/Stochastic/Distribution/HypergeometricDistribution.php
@@ -87,7 +87,7 @@ class HypergeometricDistribution
      * @param int $N Population size
      * @param int $n Number of draws
      *
-     * @return int
+     * @return float
      *
      * @todo: this can be heavily optimized
      *
@@ -98,6 +98,24 @@ class HypergeometricDistribution
         return $n * $K / $N * ($N - $K) / $N * ($N - $n) / ($N - 1);
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param int $K Successful states in the population
+     * @param int $N Population size
+     * @param int $n Number of draws
+     *
+     * @return float
+     *
+     * @todo: this can be heavily optimized
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(int $K, int $N, int $n) : float
+    {
+        return \sqrt(self::getVariance($K, $N, $n));
+    }
+
     /**
      * Get skewness.
      *
@@ -105,7 +123,7 @@ class HypergeometricDistribution
      * @param int $N Population size
      * @param int $n Number of draws
      *
-     * @return int
+     * @return float
      *
      * @todo: this can be heavily optimized
      *
@@ -124,7 +142,7 @@ class HypergeometricDistribution
      * @param int $N Population size
      * @param int $n Number of draws
      *
-     * @return int
+     * @return float
      *
      * @todo: this can be heavily optimized
      *
@@ -132,7 +150,7 @@ class HypergeometricDistribution
      */
     public static function getExKurtosis(int $K, int $N, int $n) : float
     {
-        return 1 / ($n * $K * ($N - $K) * ($N - $n) * ($N - 2) * ($N - 3))
-            * (($N - 1) * $N ** 2 * ($N * ($N + 1) - 6 * $K * ($N - $K) - 6 * $n * ($N - $n)) + 6 * $n * $K * ($N - $K) * ($N - $n) * (5 * $N - 6));
+        return (($N - 1) * $N ** 2 * ($N * ($N + 1) - 6 * $K * ($N - $K) - 6 * $n * ($N - $n)) + 6 * $n * $K * ($N - $K) * ($N - $n) * (5 * $N - 6))
+            / ($n * $K * ($N - $K) * ($N - $n) * ($N - 2) * ($N - 3));
     }
 }
diff --git a/Math/Stochastic/Distribution/LaplaceDistribution.php b/Math/Stochastic/Distribution/LaplaceDistribution.php
index f1c550f9c..72f4f1dcd 100644
--- a/Math/Stochastic/Distribution/LaplaceDistribution.php
+++ b/Math/Stochastic/Distribution/LaplaceDistribution.php
@@ -112,6 +112,20 @@ class LaplaceDistribution
         return 2 * $b ** 2;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $b Value b
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $b) : float
+    {
+        return \sqrt(self::getVariance($b));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/LogDistribution.php b/Math/Stochastic/Distribution/LogDistribution.php
index 4217de12a..34e49dc60 100644
--- a/Math/Stochastic/Distribution/LogDistribution.php
+++ b/Math/Stochastic/Distribution/LogDistribution.php
@@ -79,6 +79,20 @@ class LogDistribution
             / ((1 - $p) ** 2 * \log(1 - $p) ** 2);
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $p Value p
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $p) : float
+    {
+        return \sqrt(self::getVariance($p));
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/LogNormalDistribution.php b/Math/Stochastic/Distribution/LogNormalDistribution.php
index f764e1ee7..3a1f6003f 100644
--- a/Math/Stochastic/Distribution/LogNormalDistribution.php
+++ b/Math/Stochastic/Distribution/LogNormalDistribution.php
@@ -44,7 +44,7 @@ class LogNormalDistribution
      * Get expected value.
      *
      * @param float $mu    Mu
-     * @param float $sigma Sigma
+     * @param float $sigma Sigma = standard deviation
      *
      * @return float
      *
@@ -99,6 +99,21 @@ class LogNormalDistribution
         return (\exp($sigma ** 2) - 1) * \exp(2 * $mu + $sigma ** 2);
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $mu    Mu
+     * @param float $sigma Sigma
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $mu, float $sigma) : float
+    {
+        return \sqrt(self::getVariance($mu, $sigma));
+    }
+
     /**
      * Get skewness.
      *
diff --git a/Math/Stochastic/Distribution/LogisticDistribution.php b/Math/Stochastic/Distribution/LogisticDistribution.php
index c498474db..cf2e2fdfb 100644
--- a/Math/Stochastic/Distribution/LogisticDistribution.php
+++ b/Math/Stochastic/Distribution/LogisticDistribution.php
@@ -112,6 +112,20 @@ class LogisticDistribution
         return $s ** 2 * \M_PI ** 2 / 3;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $s s scale
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $s) : float
+    {
+        return \sqrt(self::getVariance($s));
+    }
+
     /**
      * Get skewness.
      *
diff --git a/Math/Stochastic/Distribution/NormalDistribution.php b/Math/Stochastic/Distribution/NormalDistribution.php
index 0f3697985..0bdc4e396 100644
--- a/Math/Stochastic/Distribution/NormalDistribution.php
+++ b/Math/Stochastic/Distribution/NormalDistribution.php
@@ -133,6 +133,20 @@ class NormalDistribution
         return $sig ** 2;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $sig Sigma
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $sig) : float
+    {
+        return $sig;
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/ParetoDistribution.php b/Math/Stochastic/Distribution/ParetoDistribution.php
index 570b7ea34..c1f9ba921 100644
--- a/Math/Stochastic/Distribution/ParetoDistribution.php
+++ b/Math/Stochastic/Distribution/ParetoDistribution.php
@@ -55,6 +55,21 @@ class ParetoDistribution
         return 1 - ($xm / $x) ** $alpha;
     }
 
+    /**
+     * Get expected value.
+     *
+     * @param float $xm    Lower bound
+     * @param float $alpha Alpha shape
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getMean(float $xm, float $alpha) : float
+    {
+        return $alpha > 1 ? $alpha * $xm / ($alpha - 1) : \PHP_FLOAT_MAX;
+    }
+
     /**
      * Get median
      *
@@ -96,11 +111,22 @@ class ParetoDistribution
      */
     public static function getVariance(float $xm, float $alpha) : float
     {
-        if ($alpha < 2) {
-            return \PHP_FLOAT_MAX;
-        }
+        return $alpha < 3 ? \PHP_FLOAT_MAX : $xm ** 2 * $alpha / (($alpha - 1) ** 2 * ($alpha - 2));
+    }
 
-        return $xm ** 2 * $alpha / (($alpha - 1) ** 2 * ($alpha - 2));
+    /**
+     * Get standard deviation
+     *
+     * @param float $xm    Lower bound
+     * @param float $alpha Alpha shape
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $xm, float $alpha) : float
+    {
+        return \sqrt(self::getVariance($xm, $alpha));
     }
 
     /**
@@ -114,11 +140,7 @@ class ParetoDistribution
      */
     public static function getSkewness(float $alpha) : float
     {
-        if ($alpha < 4) {
-            return 0.0;
-        }
-
-        return 2 * (1 + $alpha) / ($alpha - 3) * \sqrt(($alpha - 2) / $alpha);
+        return $alpha < 4 ? 0.0 : 2 * (1 + $alpha) / ($alpha - 3) * \sqrt(($alpha - 2) / $alpha);
     }
 
     /**
diff --git a/Math/Stochastic/Distribution/PoissonDistribution.php b/Math/Stochastic/Distribution/PoissonDistribution.php
index a452d43a4..4e87be2bc 100644
--- a/Math/Stochastic/Distribution/PoissonDistribution.php
+++ b/Math/Stochastic/Distribution/PoissonDistribution.php
@@ -121,6 +121,20 @@ class PoissonDistribution
         return $lambda;
     }
 
+    /**
+     * Get standard deviation.
+     *
+     * @param float $lambda Lambda
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $lambda) : float
+    {
+        return \sqrt($lambda);
+    }
+
     /**
      * Get moment generating function.
      *
diff --git a/Math/Stochastic/Distribution/TDistribution.php b/Math/Stochastic/Distribution/TDistribution.php
index 454c5c47d..d2f77d345 100644
--- a/Math/Stochastic/Distribution/TDistribution.php
+++ b/Math/Stochastic/Distribution/TDistribution.php
@@ -27,7 +27,7 @@ class TDistribution
     /**
      * Get expected value.
      *
-     * @return float
+     * @return int
      *
      * @since 1.0.0
      */
@@ -83,10 +83,34 @@ class TDistribution
      */
     public static function getVariance(int $nu) : float
     {
-        if ($nu < 2) {
-            return \PHP_FLOAT_MAX;
-        }
+        return $nu < 3 ? \PHP_FLOAT_MAX : $nu / ($nu - 2);
+    }
 
-        return $nu / ($nu - 2);
+    /**
+     * Get standard deviation.
+     *
+     * @param int $nu Degrees of freedom
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(int $nu) : float
+    {
+        return $nu < 3 ? \PHP_FLOAT_MAX : \sqrt(self::getVariance($nu));
+    }
+
+    /**
+     * Get Ex. kurtosis.
+     *
+     * @param float $nu Degrees of freedom
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getExKurtosis(float $nu) : float
+    {
+        return $nu < 5 && $nu > 2 ? \PHP_FLOAT_MAX : 6 / ($nu - 4);
     }
 }
diff --git a/Math/Stochastic/Distribution/UniformDistributionContinuous.php b/Math/Stochastic/Distribution/UniformDistributionContinuous.php
index 4b0c96333..11a268c1d 100644
--- a/Math/Stochastic/Distribution/UniformDistributionContinuous.php
+++ b/Math/Stochastic/Distribution/UniformDistributionContinuous.php
@@ -162,4 +162,19 @@ class UniformDistributionContinuous
     {
         return 1 / 12 * ($b - $a) ** 2;
     }
+
+    /**
+     * Get standard deviation.
+     *
+     * @param float $a Value a
+     * @param float $b Value b
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $a, float $b) : float
+    {
+        return \sqrt(self::getVariance($a, $b));
+    }
 }
diff --git a/Math/Stochastic/Distribution/UniformDistributionDiscrete.php b/Math/Stochastic/Distribution/UniformDistributionDiscrete.php
index 434ef9a0d..4496327cb 100644
--- a/Math/Stochastic/Distribution/UniformDistributionDiscrete.php
+++ b/Math/Stochastic/Distribution/UniformDistributionDiscrete.php
@@ -151,4 +151,19 @@ class UniformDistributionDiscrete
     {
         return (($b - $a + 1) ** 2 - 1) / 12;
     }
+
+    /**
+     * Get standard deviation.
+     *
+     * @param float $a Value a
+     * @param float $b Value b
+     *
+     * @return float
+     *
+     * @since 1.0.0
+     */
+    public static function getStandardDeviation(float $a, float $b) : float
+    {
+        return \sqrt(self::getVariance($a, $b));
+    }
 }
diff --git a/Math/Stochastic/Distribution/WeibullDistribution.php b/Math/Stochastic/Distribution/WeibullDistribution.php
index 9b5d82422..84f6e8a32 100644
--- a/Math/Stochastic/Distribution/WeibullDistribution.php
+++ b/Math/Stochastic/Distribution/WeibullDistribution.php
@@ -36,11 +36,7 @@ class WeibullDistribution
      */
     public static function getPdf(float $x, float $lambda, float $k) : float
     {
-        if ($x < 0) {
-            return 0.0;
-        }
-
-        return $k / $lambda * \pow($x / $lambda, $k - 1) * \exp(-($x / $lambda) ** $k);
+        return $x < 0.0 ? 0.0 : $k / $lambda * \pow($x / $lambda, $k - 1) * \exp(-($x / $lambda) ** $k);
     }
 
     /**
@@ -56,11 +52,7 @@ class WeibullDistribution
      */
     public static function getCdf(float $x, float $lambda, float $k) : float
     {
-        if ($x < 0) {
-            return 0.0;
-        }
-
-        return 1 - \exp(-($x / $lambda) ** $k);
+        return $x < 0.0 ? 0.0 : 1 - \exp(-($x / $lambda) ** $k);
     }
 
     /**
diff --git a/tests/DataStorage/Database/DatabaseExceptionFactoryTest.php b/tests/DataStorage/Database/DatabaseExceptionFactoryTest.php
deleted file mode 100644
index fb97394c5..000000000
--- a/tests/DataStorage/Database/DatabaseExceptionFactoryTest.php
+++ /dev/null
@@ -1,33 +0,0 @@
-<?php
-/**
- * Orange Management
- *
- * PHP Version 7.4
- *
- * @package   tests
- * @copyright Dennis Eichhorn
- * @license   OMS License 1.0
- * @version   1.0.0
- * @link      https://orange-management.org
- */
-declare(strict_types=1);
-
-namespace phpOMS\tests\DataStorage\Database;
-
-use phpOMS\DataStorage\Database\DatabaseExceptionFactory;
-
-/**
- * @internal
- */
-class DatabaseExceptionFactoryTest extends \PHPUnit\Framework\TestCase
-{
-    public function testException() : void
-    {
-        self::assertEquals('\PDOException', DatabaseExceptionFactory::createException(new \PDOException()));
-    }
-
-    public function testExceptionMessage() : void
-    {
-        self::assertEquals('', DatabaseExceptionFactory::createExceptionMessage(new \PDOException()));
-    }
-}
diff --git a/tests/DataStorage/Database/Query/ExpressionTest.php b/tests/DataStorage/Database/Query/ExpressionTest.php
index 43564b7e6..c9153799a 100644
--- a/tests/DataStorage/Database/Query/ExpressionTest.php
+++ b/tests/DataStorage/Database/Query/ExpressionTest.php
@@ -14,13 +14,15 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\DataStorage\Database\Query;
 
+use phpOMS\DataStorage\Database\Query\Expression;
+
 /**
  * @internal
  */
 class ExpressionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testDefault() : void
     {
-        self::markTestIncomplete();
+        self::assertInstanceOf('\phpOMS\DataStorage\Database\Query\Builder', new Expression($GLOBALS['dbpool']->get()));
     }
 }
diff --git a/tests/DataStorage/Database/Schema/Exception/TableExceptionTest.php b/tests/DataStorage/Database/Schema/Exception/TableExceptionTest.php
deleted file mode 100644
index c20d6ebf5..000000000
--- a/tests/DataStorage/Database/Schema/Exception/TableExceptionTest.php
+++ /dev/null
@@ -1,26 +0,0 @@
-<?php
-/**
- * Orange Management
- *
- * PHP Version 7.4
- *
- * @package   tests
- * @copyright Dennis Eichhorn
- * @license   OMS License 1.0
- * @version   1.0.0
- * @link      https://orange-management.org
- */
-declare(strict_types=1);
-
-namespace phpOMS\tests\DataStorage\Database\Schema\Exception;
-
-/**
- * @internal
- */
-class TableExceptionTest extends \PHPUnit\Framework\TestCase
-{
-    public function testPlaceholder() : void
-    {
-        self::markTestIncomplete();
-    }
-}
diff --git a/tests/Math/Matrix/MatrixTest.php b/tests/Math/Matrix/MatrixTest.php
index abc816429..f85726e08 100644
--- a/tests/Math/Matrix/MatrixTest.php
+++ b/tests/Math/Matrix/MatrixTest.php
@@ -184,6 +184,7 @@ class MatrixTest extends \PHPUnit\Framework\TestCase
     public function testReduce() : void
     {
         self::assertEquals([[-6, -7], [0, -5]], $this->C->upperTriangular()->getMatrix());
+        self::markTestIncomplete();
         //self::assertEquals([], $this->C->lowerTriangular()->getMatrix());
         //self::assertEquals([], $this->C->diagonalize()->getMatrix());
     }
diff --git a/tests/Math/Stochastic/Distribution/BernoulliDistributionTest.php b/tests/Math/Stochastic/Distribution/BernoulliDistributionTest.php
index 51f5a6edf..90ca38dfc 100644
--- a/tests/Math/Stochastic/Distribution/BernoulliDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/BernoulliDistributionTest.php
@@ -61,6 +61,14 @@ class BernoulliDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEqualsWithDelta($p * $q, BernoulliDistribution::getVariance($p), 0.01);
     }
 
+    public function testStandardDeviation() : void
+    {
+        $p = 0.3;
+        $q = 1 - $p;
+
+        self::assertEqualsWithDelta(\sqrt($p * $q), BernoulliDistribution::getStandardDeviation($p), 0.01);
+    }
+
     public function testSkewness() : void
     {
         $p = 0.3;
diff --git a/tests/Math/Stochastic/Distribution/BetaDistributionTest.php b/tests/Math/Stochastic/Distribution/BetaDistributionTest.php
index d16c074eb..63e40850f 100644
--- a/tests/Math/Stochastic/Distribution/BetaDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/BetaDistributionTest.php
@@ -14,13 +14,45 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\BetaDistribution;
+
 /**
  * @internal
  */
 class BetaDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testMean() : void
     {
-        self::markTestIncomplete();
+        self::assertEquals(1 / 2, BetaDistribution::getMean(2.0, 2.0));
+    }
+
+    public function testMode() : void
+    {
+        self::assertEquals(1 / 2, BetaDistribution::getMode(2.0, 2.0));
+        self::assertEqualsWithDelta(0.2, BetaDistribution::getMode(2.0, 5.0), 0.1);
+        self::assertEquals(0.0, BetaDistribution::getMode(1.0, 2.0));
+        self::assertEquals(1.0, BetaDistribution::getMode(1.0, 1.0));
+    }
+
+    public function testVariance() : void
+    {
+        self::assertEqualsWithDelta(1 / 20, BetaDistribution::getVariance(2.0, 2.0), 0.001);
+    }
+
+    public function testStandardDeviation() : void
+    {
+        self::assertEqualsWithDelta(\sqrt(1 / 20), BetaDistribution::getStandardDeviation(2.0, 2.0), 0.001);
+    }
+
+    public function testSkewness() : void
+    {
+        self::assertEqualsWithDelta(0, BetaDistribution::getSkewness(2.0, 2.0), 0.001);
+        self::assertEqualsWithDelta(0.565685, BetaDistribution::getSkewness(1.0, 2.0), 0.001);
+        self::assertEqualsWithDelta(-0.565685, BetaDistribution::getSkewness(2.0, 1.0), 0.001);
+    }
+
+    public function testExKurtosis() : void
+    {
+        self::assertEqualsWithDelta(-6 / 7, BetaDistribution::getExKurtosis(2.0, 2.0), 0.001);
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/BinomialDistributionTest.php b/tests/Math/Stochastic/Distribution/BinomialDistributionTest.php
index e3ab6cc54..a60629372 100644
--- a/tests/Math/Stochastic/Distribution/BinomialDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/BinomialDistributionTest.php
@@ -71,6 +71,14 @@ class BinomialDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEqualsWithDelta($n * $p * (1 - $p), BinomialDistribution::getVariance($n, $p), 0.01);
     }
 
+    public function testStandardDeviation() : void
+    {
+        $n = 20;
+        $p = 0.4;
+
+        self::assertEqualsWithDelta(\sqrt($n * $p * (1 - $p)), BinomialDistribution::getStandardDeviation($n, $p), 0.01);
+    }
+
     public function testSkewness() : void
     {
         $n = 20;
diff --git a/tests/Math/Stochastic/Distribution/ChiSquaredDistributionTest.php b/tests/Math/Stochastic/Distribution/ChiSquaredDistributionTest.php
index 428c168b4..2c384e988 100644
--- a/tests/Math/Stochastic/Distribution/ChiSquaredDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/ChiSquaredDistributionTest.php
@@ -67,6 +67,13 @@ class ChiSquaredDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEquals(2 * $df, ChiSquaredDistribution::getVariance($df));
     }
 
+    public function testStandardDeviation() : void
+    {
+        $df = 5;
+
+        self::assertEquals(\sqrt(2 * $df), ChiSquaredDistribution::getStandardDeviation($df));
+    }
+
     public function testMedian() : void
     {
         $df = 5;
diff --git a/tests/Math/Stochastic/Distribution/ExponentialDistributionTest.php b/tests/Math/Stochastic/Distribution/ExponentialDistributionTest.php
index e80a5ce5d..7c27315a4 100644
--- a/tests/Math/Stochastic/Distribution/ExponentialDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/ExponentialDistributionTest.php
@@ -65,6 +65,11 @@ class ExponentialDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEquals(1/(3 ** 2), ExponentialDistribution::getVariance(3));
     }
 
+    public function testStandardDeviation() : void
+    {
+        self::assertEquals(\sqrt(1/(3 ** 2)), ExponentialDistribution::getStandardDeviation(3));
+    }
+
     public function testExKurtosis() : void
     {
         self::assertEquals(6, ExponentialDistribution::getExKurtosis());
diff --git a/tests/Math/Stochastic/Distribution/GammaDistributionTest.php b/tests/Math/Stochastic/Distribution/GammaDistributionTest.php
index 7e0d21c1c..5d81acaee 100644
--- a/tests/Math/Stochastic/Distribution/GammaDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/GammaDistributionTest.php
@@ -14,13 +14,41 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\GammaDistribution;
+
 /**
  * @internal
  */
 class GammaDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testPDFIntegerK() : void
     {
-        self::markTestIncomplete();
+        self::assertEqualsWithDelta(\exp(-1), GammaDistribution::getPdfIntegerK(1, 1, 1), 0.001);
+        self::assertEqualsWithDelta(3 * \exp(-3/4) / 16, GammaDistribution::getPdfIntegerK(3, 2, 4), 0.001);
+    }
+
+    public function testMeanK() : void
+    {
+        self::assertEqualsWithDelta(8, GammaDistribution::getMeanK(2, 4), 0.001);
+    }
+
+    public function testVarianceK() : void
+    {
+        self::assertEqualsWithDelta(32, GammaDistribution::getVarianceK(2, 4), 0.001);
+    }
+
+    public function testStandardDeviationK() : void
+    {
+        self::assertEqualsWithDelta(\sqrt(32), GammaDistribution::getStandardDeviationK(2, 4), 0.001);
+    }
+
+    public function testExKurtosis() : void
+    {
+        self::assertEqualsWithDelta(3, GammaDistribution::getExKurtosis(2, 4), 0.001);
+    }
+
+    public function testSkewness() : void
+    {
+        self::assertEqualsWithDelta(\sqrt(2), GammaDistribution::getSkewness(2, 4), 0.001);
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/GeometricDistributionTest.php b/tests/Math/Stochastic/Distribution/GeometricDistributionTest.php
index 6a2fee4cc..3e8b93b37 100644
--- a/tests/Math/Stochastic/Distribution/GeometricDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/GeometricDistributionTest.php
@@ -56,6 +56,13 @@ class GeometricDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEquals((1 - $p) / $p ** 2, GeometricDistribution::getVariance($p));
     }
 
+    public function testgetStandardDeviation() : void
+    {
+        $p = 0.3;
+
+        self::assertEquals(\sqrt((1 - $p) / $p ** 2), GeometricDistribution::getStandardDeviation($p));
+    }
+
     public function testSkewness() : void
     {
         $p = 0.3;
diff --git a/tests/Math/Stochastic/Distribution/HypergeometricDistributionTest.php b/tests/Math/Stochastic/Distribution/HypergeometricDistributionTest.php
index 570be815b..325e97c50 100644
--- a/tests/Math/Stochastic/Distribution/HypergeometricDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/HypergeometricDistributionTest.php
@@ -14,13 +14,35 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\HypergeometricDistribution;
+
 /**
  * @internal
  */
 class HypergeometricDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testMean() : void
     {
-        self::markTestIncomplete();
+        self::assertEquals(9, HypergeometricDistribution::getMean(15, 20, 12));
+    }
+
+    public function testVariance() : void
+    {
+        self::assertEqualsWithDelta(0.973328526784575 ** 2, HypergeometricDistribution::getVariance(15, 20, 12), 0.001);
+    }
+
+    public function testStandardDeviation() : void
+    {
+        self::assertEqualsWithDelta(0.973328526784575, HypergeometricDistribution::getStandardDeviation(15, 20, 12), 0.001);
+    }
+
+    public function testSkewness() : void
+    {
+        self::assertEqualsWithDelta(0.114156, HypergeometricDistribution::getSkewness(15, 20, 12), 0.001);
+    }
+
+    public function testExKurtosis() : void
+    {
+        self::assertEqualsWithDelta(-0.247277, HypergeometricDistribution::getExKurtosis(15, 20, 12), 0.001);
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/LaplaceDistributionTest.php b/tests/Math/Stochastic/Distribution/LaplaceDistributionTest.php
index f3bec8ba5..da7b6f704 100644
--- a/tests/Math/Stochastic/Distribution/LaplaceDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/LaplaceDistributionTest.php
@@ -71,6 +71,13 @@ class LaplaceDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEquals(2 * $b ** 2, LaplaceDistribution::getVariance($b));
     }
 
+    public function testStandardDeviation() : void
+    {
+        $b = 3;
+
+        self::assertEquals(\sqrt(2 * $b ** 2), LaplaceDistribution::getStandardDeviation($b));
+    }
+
     public function testMgf() : void
     {
         $t = 2;
diff --git a/tests/Math/Stochastic/Distribution/LogNormalDistributionTest.php b/tests/Math/Stochastic/Distribution/LogNormalDistributionTest.php
index cb7983937..542186205 100644
--- a/tests/Math/Stochastic/Distribution/LogNormalDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/LogNormalDistributionTest.php
@@ -14,13 +14,41 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\LogNormalDistribution;
+
 /**
  * @internal
  */
 class LogNormalDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testPdf() : void
     {
-        self::markTestIncomplete();
+        self::assertEqualsWithDelta(0.060069054, LogNormalDistribution::getPdf(3, 2, 2), 0.001);
+    }
+
+    public function testMean() : void
+    {
+        self::assertEqualsWithDelta(\exp(13/2), LogNormalDistribution::getMean(2, 3), 0.001);
+    }
+
+    public function testVariance() : void
+    {
+        self::assertEqualsWithDelta((\exp(9) - 1) * \exp(13), LogNormalDistribution::getVariance(2, 3), 0.001);
+    }
+
+    public function testStandardDeviation() : void
+    {
+        self::assertEqualsWithDelta(\exp(13/2) * \sqrt(\exp(9) - 1), LogNormalDistribution::getStandardDeviation(2, 3), 0.001);
+        self::assertEqualsWithDelta(\sqrt((\exp(9) - 1) * \exp(13)), LogNormalDistribution::getStandardDeviation(2, 3), 0.001);
+    }
+
+    public function testSkewness() : void
+    {
+        self::assertEqualsWithDelta(\sqrt(\exp(9) - 1) * (\exp(9) + 2), LogNormalDistribution::getSkewness(3), 0.001);
+    }
+
+    public function testExKurtosis() : void
+    {
+        self::assertEqualsWithDelta(\exp(16) + 2 * \exp(12) + 3 * \exp(8) - 6, LogNormalDistribution::getExKurtosis(2), 0.001);
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/NormalDistributionTest.php b/tests/Math/Stochastic/Distribution/NormalDistributionTest.php
index 8f41ed832..cc266b876 100644
--- a/tests/Math/Stochastic/Distribution/NormalDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/NormalDistributionTest.php
@@ -76,4 +76,11 @@ class NormalDistributionTest extends \PHPUnit\Framework\TestCase
 
         self::assertEquals($sig ** 2, NormalDistribution::getVariance($sig));
     }
+
+    public function testStandardDeviation() : void
+    {
+        $sig = 0.8;
+
+        self::assertEquals($sig, NormalDistribution::getStandardDeviation($sig));
+    }
 }
diff --git a/tests/Math/Stochastic/Distribution/ParetoDistributionTest.php b/tests/Math/Stochastic/Distribution/ParetoDistributionTest.php
index 99d2323d3..a607fc5f8 100644
--- a/tests/Math/Stochastic/Distribution/ParetoDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/ParetoDistributionTest.php
@@ -14,13 +14,49 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\ParetoDistribution;
+
 /**
  * @internal
  */
 class ParetoDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testPdf() : void
     {
-        self::markTestIncomplete();
+        self::assertEqualsWithDelta(0.263374485596, ParetoDistribution::getPdf(3, 2, 4), 0.001);
+    }
+
+    public function testCdf() : void
+    {
+        self::assertEqualsWithDelta(0.8024691358, ParetoDistribution::getCdf(3, 2, 4), 0.001);
+    }
+
+    public function testMean() : void
+    {
+        self::assertEqualsWithDelta(8 / 3, ParetoDistribution::getMean(2, 4), 0.001);
+        self::assertEquals(\PHP_FLOAT_MAX, ParetoDistribution::getMean(2, 1));
+    }
+
+    public function testVariance() : void
+    {
+        self::assertEqualsWithDelta(2, ParetoDistribution::getVariance(3, 4), 0.001);
+        self::assertEqualsWithDelta(\PHP_FLOAT_MAX, ParetoDistribution::getVariance(3, 2), 0.001);
+    }
+
+    public function testStandardDeviation() : void
+    {
+        self::assertEqualsWithDelta(\sqrt(2), ParetoDistribution::getStandardDeviation(3, 4), 0.001);
+    }
+
+    public function testExKurtosis() : void
+    {
+        self::assertEqualsWithDelta(35.666666666666664, ParetoDistribution::getExKurtosis(6, 5), 0.001);
+        self::assertEquals(0.0, ParetoDistribution::getExKurtosis(4));
+    }
+
+    public function testSkewness() : void
+    {
+        self::assertEqualsWithDelta(3.810317377662722, ParetoDistribution::getSkewness(6, 5), 0.001);
+        self::assertEquals(0.0, ParetoDistribution::getSkewness(3));
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/PoissonDistributionTest.php b/tests/Math/Stochastic/Distribution/PoissonDistributionTest.php
index 6addd2dd6..1ea07ba2f 100644
--- a/tests/Math/Stochastic/Distribution/PoissonDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/PoissonDistributionTest.php
@@ -58,6 +58,13 @@ class PoissonDistributionTest extends \PHPUnit\Framework\TestCase
         self::assertEquals($l, PoissonDistribution::getVariance($l));
     }
 
+    public function testStandardDeviation() : void
+    {
+        $l = 4.6;
+
+        self::assertEquals(\sqrt($l), PoissonDistribution::getStandardDeviation($l));
+    }
+
     public function testSkewness() : void
     {
         $l = 4.6;
diff --git a/tests/Math/Stochastic/Distribution/TDistributionTest.php b/tests/Math/Stochastic/Distribution/TDistributionTest.php
index 7c1685ebf..19832ca9e 100644
--- a/tests/Math/Stochastic/Distribution/TDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/TDistributionTest.php
@@ -14,13 +14,48 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\TDistribution;
+
 /**
  * @internal
  */
 class TDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testMean() : void
     {
-        self::markTestIncomplete();
+        self::assertEquals(0, TDistribution::getMean());
+    }
+
+    public function testMedian() : void
+    {
+        self::assertEquals(0, TDistribution::getMedian());
+    }
+
+    public function testMode() : void
+    {
+        self::assertEquals(0, TDistribution::getMode());
+    }
+
+    public function testVariance() : void
+    {
+        self::assertEqualsWithDelta(5/3, TDistribution::getVariance(5), 0.001);
+        self::assertEqualsWithDelta(\PHP_FLOAT_MAX, TDistribution::getVariance(2), 0.001);
+    }
+
+    public function testStandardDeviation() : void
+    {
+        self::assertEqualsWithDelta(\sqrt(5/3), TDistribution::getStandardDeviation(5), 0.001);
+        self::assertEqualsWithDelta(\PHP_FLOAT_MAX, TDistribution::getStandardDeviation(2), 0.001);
+    }
+
+    public function testExKurtosis() : void
+    {
+        self::assertEqualsWithDelta(6, TDistribution::getExKurtosis(5), 0.001);
+        self::assertEqualsWithDelta(\PHP_FLOAT_MAX, TDistribution::getExKurtosis(3), 0.001);
+    }
+
+    public function testSkewness() : void
+    {
+        self::assertEquals(0, TDistribution::getSkewness());
     }
 }
diff --git a/tests/Math/Stochastic/Distribution/UniformDistributionContinuousTest.php b/tests/Math/Stochastic/Distribution/UniformDistributionContinuousTest.php
index 08b4c1d83..3e208a1f0 100644
--- a/tests/Math/Stochastic/Distribution/UniformDistributionContinuousTest.php
+++ b/tests/Math/Stochastic/Distribution/UniformDistributionContinuousTest.php
@@ -80,6 +80,14 @@ class UniformDistributionContinuousTest extends \PHPUnit\Framework\TestCase
         self::assertEquals(1 / 12 * ($b - $a) ** 2, UniformDistributionContinuous::getVariance($a, $b));
     }
 
+    public function testStandardDeviation() : void
+    {
+        $a = 1;
+        $b = 4;
+
+        self::assertEquals(\sqrt(1 / 12 * ($b - $a) ** 2), UniformDistributionContinuous::getStandardDeviation($a, $b));
+    }
+
     public function testSkewness() : void
     {
         self::assertEquals(0, UniformDistributionContinuous::getSkewness());
diff --git a/tests/Math/Stochastic/Distribution/UniformDistributionDiscreteTest.php b/tests/Math/Stochastic/Distribution/UniformDistributionDiscreteTest.php
index cb1d54445..b6326bb39 100644
--- a/tests/Math/Stochastic/Distribution/UniformDistributionDiscreteTest.php
+++ b/tests/Math/Stochastic/Distribution/UniformDistributionDiscreteTest.php
@@ -67,6 +67,14 @@ class UniformDistributionDiscreteTest extends \PHPUnit\Framework\TestCase
         self::assertEquals((($b - $a + 1) ** 2 - 1) / 12, UniformDistributionDiscrete::getVariance($a, $b));
     }
 
+    public function testStandardDeviation() : void
+    {
+        $a = 1;
+        $b = 4;
+
+        self::assertEquals(\sqrt((($b - $a + 1) ** 2 - 1) / 12), UniformDistributionDiscrete::getStandardDeviation($a, $b));
+    }
+
     public function testExKurtosis() : void
     {
         $a = 1;
diff --git a/tests/Math/Stochastic/Distribution/WeibullDistributionTest.php b/tests/Math/Stochastic/Distribution/WeibullDistributionTest.php
index 4b431924f..7b4207dce 100644
--- a/tests/Math/Stochastic/Distribution/WeibullDistributionTest.php
+++ b/tests/Math/Stochastic/Distribution/WeibullDistributionTest.php
@@ -14,13 +14,22 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Math\Stochastic\Distribution;
 
+use phpOMS\Math\Stochastic\Distribution\WeibullDistribution;
+
 /**
  * @internal
  */
 class WeibullDistributionTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testPdf() : void
     {
-        self::markTestIncomplete();
+        self::assertEqualsWithDelta(0.213668559, WeibullDistribution::getPdf(3, 4, 2), 0.001);
+        self::assertEqualsWithDelta(0.0, WeibullDistribution::getPdf(-1, 4, 2), 0.001);
+    }
+
+    public function testCdf() : void
+    {
+        self::assertEqualsWithDelta(0.430217175, WeibullDistribution::getCdf(3, 4, 2), 0.001);
+        self::assertEqualsWithDelta(0.0, WeibullDistribution::getCdf(-1, 4, 2), 0.001);
     }
 }
diff --git a/tests/Stdlib/Base/NullLocationTest.php b/tests/Stdlib/Base/NullLocationTest.php
index 5638dec3f..b31c0c6e7 100644
--- a/tests/Stdlib/Base/NullLocationTest.php
+++ b/tests/Stdlib/Base/NullLocationTest.php
@@ -14,13 +14,15 @@ declare(strict_types=1);
 
 namespace phpOMS\tests\Stdlib\Base;
 
+use phpOMS\Stdlib\Base\NullLocation;
+
 /**
  * @internal
  */
 class NullLocationTest extends \PHPUnit\Framework\TestCase
 {
-    public function testPlaceholder() : void
+    public function testNullLocation() : void
     {
-        self::markTestIncomplete();
+        self::assertInstanceOf('\phpOMS\Stdlib\Base\Location', new NullLocation());
     }
 }