diff --git a/tests/Probability/Distribution/Continuous/StudentTTest.php b/tests/Probability/Distribution/Continuous/StudentTTest.php
index <HASH>..<HASH> 100644
--- a/tests/Probability/Distribution/Continuous/StudentTTest.php
+++ b/tests/Probability/Distribution/Continuous/StudentTTest.php
@@ -74,12 +74,16 @@ class StudentTTest extends \PHPUnit_Framework_TestCase
     public function dataProviderForMean()
     {
         return [
-            [1, null],
             [2, 0],
             [3, 0],
         ];
     }
     
+    public function testMeanNAN()
+    {
+        $this->assertNan(StudentT::mean(1));
+    }
+    
     /**
      * @dataProvider dataProviderForInverse
      */
update mean of StudentT to NAN if v<1

was null