Fix for the missing denominator in an example in the PyMC3 version of Chapter4

Author: Sachintha Karunaratne

Chapter4_TheGreatestTheoremNeverTold/Ch4_LawOfLargeNumbers_PyMC3.ipynb

@@ -233,7 +233,7 @@
     "Again, this is fairly obvious after a moments thought: the indicator function is only 1 if the event occurs, so we are summing only the times the event occurs and dividing by the total number of trials  (consider how we usually approximate probabilities using frequencies). For example, suppose we wish to estimate the probability that a $Z \\sim Exp(.5)$ is greater than 5, and we have many samples from a $Exp(.5)$ distribution. \n",
     "\n",
     "\n",
-    "$$ P( Z > 5 ) =  \\sum_{i=1}^N \\mathbb{1}_{z > 5 }(Z_i) $$\n"
+    "$$ P( Z > 5 ) =  \\frac{1}{N}\\sum_{i=1}^N \\mathbb{1}_{z > 5 }(Z_i) $$\n"
    ]
   },
   {
@@ -1193,21 +1193,21 @@
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   "anaconda-cloud": {},
   "kernelspec": {
-   "display_name": "Python 2",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "python2"
+   "name": "python3"
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   "language_info": {
    "codemirror_mode": {
     "name": "ipython",
-    "version": 2
+    "version": 3
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    "file_extension": ".py",
    "mimetype": "text/x-python",
    "name": "python",
    "nbconvert_exporter": "python",
-   "pygments_lexer": "ipython2",
-   "version": "2.7.11"
+   "pygments_lexer": "ipython3",
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