# HG changeset patch
# User Oleksandr Gavenko <gavenkoa@gmail.com>
# Date 1458137891 -7200
# Node ID 60353d4d994d619514da29c17ef01b888fd8bca6
# Parent  5d6cec5fe095f5c289fc193d37cfa8d8fb7fdd33
PMF properties.

diff -r 5d6cec5fe095 -r 60353d4d994d probability-discrete.rst
--- a/probability-discrete.rst	Wed Mar 16 14:00:04 2016 +0200
+++ b/probability-discrete.rst	Wed Mar 16 16:18:11 2016 +0200
@@ -21,6 +21,12 @@
 
    PMF(X = x) = P(X = x) = p_X(x) = P({ω ∈ Ω: X(ω) = x})
 
+   PMF(a ≤ X ≤ b) = P(a ≤ X ≤ b) = ∑_{a ≤ x ≤ b} P(X = x)
+
+   p_X(x) ≥ 0
+
+   ∑_x p_X(x) = 1
+
 where :math:`X` is a random variable on space :math:`Ω` of outcomes which mapped
 to real number via :math:`X(ω)`.