diff --git a/1-Introduction/04-stats-and-probability/notebook.ipynb b/1-Introduction/04-stats-and-probability/notebook.ipynb
index dabf91c7..423404dc 100644
--- a/1-Introduction/04-stats-and-probability/notebook.ipynb
+++ b/1-Introduction/04-stats-and-probability/notebook.ipynb
@@ -487,7 +487,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "np.corrcoef(df['Height'],df['Weight'])"
+    "np.corrcoef(df['Height'].ffill(),df['Weight'])"
    ]
   },
   {