Minor changes

source/statistics/notations.rst

@@ -14,7 +14,7 @@ A *population* is the entire population that you want to analyze. It is a exhaus
 
 *Statistics* allows you to infers properties on a population using samples with a certain degree of confidence.
 
-Notation: A Schizophrenia story
+Notation: Tale of Schizophrenia
 ================================
 Two different notation conventions are used. The one to use depends if you are working on a *population* or a *sample*:
 
@@ -27,4 +27,17 @@ Two different notation conventions are used. The one to use depends if you are w
     * - Sample mean
       - :math:`\mu`
       - :math:`\overline{x}`
+    * - Variance
+      - :math:`\sigma^2`
+      - :math:`s^2`
+    * - Standard deviation
+      - :math:`\sigma`
+      - :math:`s`
+
+Operators
+==========
+
+Var esperance etc.. + remove in metrics esperence
+   
+