diff --git a/Notebooks/Chap21/21_1_Bias_Mitigation.ipynb b/Notebooks/Chap21/21_1_Bias_Mitigation.ipynb
index ad197ef..cda001d 100644
--- a/Notebooks/Chap21/21_1_Bias_Mitigation.ipynb
+++ b/Notebooks/Chap21/21_1_Bias_Mitigation.ipynb
@@ -71,7 +71,7 @@
       "cell_type": "code",
       "source": [
         "# Class that can describe interesting curve shapes based on the input parameters\n",
-        "# Details dont' matter\n",
+        "# Details don't matter\n",
         "class FreqCurve:\n",
         "  def __init__(self, weight, mean1, mean2, sigma1, sigma2, prop):\n",
         "    self.mean1 = mean1\n",
@@ -438,4 +438,4 @@
       }
     }
   ]
-}
\ No newline at end of file
+}