diff --git a/source/statistics/tests/index.rst b/source/statistics/tests/index.rst
index c285f40..c6713be 100644
--- a/source/statistics/tests/index.rst
+++ b/source/statistics/tests/index.rst
@@ -14,6 +14,9 @@ Statistical tests are used to decide whether a hypotesis is true or not. To do s
    - The mean of two populations are differents
    - The average weight of the children in that school differ from the one of the country
 
+.. note::
+
+   :math:`H_1` can also be noted :math:`H_a` (alternative hypothesis).
 
 A statistical test usually works with a **p-value** noted :math:`\alpha`.
 It corresponds to the probability of obtaining the results that you have under the assumption that the null hypothesis is correct.