diff --git a/source/statistics/metrics.rst b/source/statistics/metrics.rst
index c86ef8a..1433fe4 100644
--- a/source/statistics/metrics.rst
+++ b/source/statistics/metrics.rst
@@ -121,9 +121,9 @@ When computing the standard deviation of :math:`X`, we have:
 .. math::
   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. In fact, by knowing :math:`n-1` of the :math:`x_i`, we can deduce the last
-one as follow:
+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.
+Otherwise, the mean changes. In fact, by knowing :math:`n-1` of the :math:`x_i`, we can deduce the last one as follow:
 
 .. math::
    \overline{x}=\frac{(\sum_{i=1}^{n-1} x_i) + x_n}{n} \Longrightarrow x_n = n\overline{x} - (\sum_{i=1}^{n-1} x_i)