diff --git a/src/itmlogic/qerf.py b/src/itmlogic/qerf.py
index 0887a3c..079d41c 100644
--- a/src/itmlogic/qerf.py
+++ b/src/itmlogic/qerf.py
@@ -1,20 +1,22 @@
+import math
+
 def qerf(z):
     """
-    The standard normal complementary probability - see function in 
+    The standard normal complementary probability - see function in
     C. Hastings, Jr. (1955). The maximum error should be 7.5x10^-8.
 
     Parameters
     ----------
     z : TODO: Type
         TODO: Description
-    
+
     Output
     ------
     qerf1 : float
         TODO:
 
     """
-    
+
     b1 = 0.319381530
     b2 = -0.356563782
     b3 = 1.781477937
@@ -24,22 +26,23 @@ def qerf(z):
 
     rrt2pi = 0.398942280
 
-    x = z[0]
+    x = z
     t = abs(x)
 
     if t >= 10:
-    
+
         qerf1 = 0
-    
+
     else:
-    
+
         t = rp / (t + rp)
 
         qerf1 = (
-            exp(-0.5 * x**2) * rrt2pi * 
+            math.exp(-0.5 * x**2) * rrt2pi *
             ((((b5 * t + b4) * t + b3) * t + b2) * t + b1) * t
             )
 
-    # if (x<0.) qerf1=1.-qerf1  TODO:
+    if x < 0:
+        qerf1 = 1 - qerf1
 
-    return qerf1
\ No newline at end of file
+    return qerf1
diff --git a/tests/test_aknfe.py b/tests/test_aknfe.py
index 3aab128..e3b8c2b 100644
--- a/tests/test_aknfe.py
+++ b/tests/test_aknfe.py
@@ -3,8 +3,7 @@
 
 def test_aknfe():
 
+    assert round(aknfe(2), 2) == 16.36
+    assert round(aknfe(3), 2) == 17.99
     assert round(aknfe(5), 2) == 20.04
     assert round(aknfe(6), 2) == 20.73
-
-
-    
\ No newline at end of file
diff --git a/tests/test_fht.py b/tests/test_fht.py
index 04b25fa..39eaee2 100644
--- a/tests/test_fht.py
+++ b/tests/test_fht.py
@@ -12,5 +12,6 @@ def test_fht():
 
     assert actual_answer == expected_answer
 
+    assert round(fht(150, 20), 2) == 11.05
 
-    
\ No newline at end of file
+    assert round(fht(150, 1e-6), 2) == -29.96
diff --git a/tests/test_h0f.py b/tests/test_h0f.py
index f8ccf1d..ae68f18 100644
--- a/tests/test_h0f.py
+++ b/tests/test_h0f.py
@@ -12,3 +12,11 @@ def test_h0f():
     expected_answer = 34.28154717133048
 
     assert actual_answer == expected_answer
+
+    actual_answer = h0f(2, -1)
+
+    assert round(actual_answer, 2) == 9.33
+
+    actual_answer = h0f(2, 6)
+
+    assert round(actual_answer, 2) == 18.53
diff --git a/tests/test_qerf.py b/tests/test_qerf.py
index 8385b45..9ab646d 100644
--- a/tests/test_qerf.py
+++ b/tests/test_qerf.py
@@ -1,4 +1,8 @@
 import pytest
 from itmlogic.qerf import qerf
 
-# def test_qerf():
+def test_qerf():
+
+    assert round(qerf(-1),4) == 0.8413
+    assert round(qerf(1),4) == 0.1587
+    assert round(qerf(10),4) == 0