diff --git a/README.md b/README.md
index 4b438d9..c1a7b93 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ The primer is spread across a collection of [IPython Notebooks](http://ipython.o
 There are four versions of the primer. Three versions contain the entire primer in a single notebook:
 
 * Single IPython Notebook (cleared output cells): [Python_for_Data_Science_clean.ipynb](Python_for_Data_Science_clean.ipynb)
-* Single IPython Notebook (filled output cells): [Python_for_Data_Science_clean.ipynb](Python_for_Data_Science_all.ipynb)
+* Single IPython Notebook (filled output cells): [Python_for_Data_Science_all.ipynb](Python_for_Data_Science_all.ipynb)
 * Single web page (HTML): [Python_for_Data_Science_all.html](Python_for_Data_Science_all.html)
 
 The other version divides the primer into 5 separate notebooks:
@@ -56,4 +56,4 @@ There are also 2 data files, based on the [mushroom dataset](https://archive.ics
 * Changed ["call by reference"](https://en.wikipedia.org/wiki/Evaluation_strategy#Call_by_reference) to ["call by sharing"](https://en.wikipedia.org/wiki/Evaluation_strategy#Call_by_sharing)
 * Added `isinstance()` (and reference to duck typing) to section on `type()`
 * Added variable for `delimiter` rather than hard-coding `'|'` character
-* Cleaned up various cells
\ No newline at end of file
+* Cleaned up various cells
diff --git a/simple_ml.py b/simple_ml.py
index aedd741..5bb84a6 100644
--- a/simple_ml.py
+++ b/simple_ml.py
@@ -195,7 +195,7 @@ def entropy(instances, class_index=0, attribute_name=None, value_name=None):
         	'={}'.format(value_name) if value_name else ''))
     for value in value_counts:
         value_probability = value_counts[value] / num_instances
-        child_entropy = value_probability * math.log(value_probability, num_values)
+        child_entropy = value_probability * math.log(value_probability, 2)
         attribute_entropy -= child_entropy
         if attribute_name:
             print('  - p({0}) x log(p({0}), {1})  =  - {2:5.3f} x log({2:5.3f})  =  {3:5.3f}'.format(