diff --git a/source/statistics/metrics.rst b/source/statistics/metrics.rst
index fee9adf..f153571 100644
--- a/source/statistics/metrics.rst
+++ b/source/statistics/metrics.rst
@@ -87,7 +87,7 @@ Thus, the degree of freedom in this computation is :math:`n`.
 When computing the standard deviation of :math:`X`, we have:
 
 .. math::
-  \hat{\sigma}_x=\frac{\sum_{i=0}^n (x_i-\overline{x})^2}{n}
+  s^2=\frac{\sum_{i=0}^n (x_i-\overline{x})^2}{n}
 
 In this case, the degree of freedom is :math:`n-1`. As the mean is already known, only :math:`n-1`
 of the :math:`x_i` are allowed to vary. By knowing :math:`n-1` of the :math:`x_i`, we can deduce the last