diff --git a/source/statistics/notations.rst b/source/statistics/notations.rst
index ce304b6..d111887 100644
--- a/source/statistics/notations.rst
+++ b/source/statistics/notations.rst
@@ -36,6 +36,13 @@ Two different notation conventions are used. The one to use depends if you are w
       - :math:`\sigma`
       - :math:`s`
 
+To determine the metric of a population (say :math:`\mu`) using a sample, we use an estimator.
+In the case of :math:`\mu`, we use :math:`\overline{x}` as an estimator.
+
+.. note::
+   Estimators can also be denoted with the hat symbol.
+   For example :math:`\hat{\mu}\equiv\overline{x}`.
+        
 Operators
 ==========