diff --git a/lib/ex_unit/lib/ex_unit/assertions.ex b/lib/ex_unit/lib/ex_unit/assertions.ex
index bdcf4b6c917..1c2ef3cfd52 100644
--- a/lib/ex_unit/lib/ex_unit/assertions.ex
+++ b/lib/ex_unit/lib/ex_unit/assertions.ex
@@ -670,11 +670,14 @@ defmodule ExUnit.Assertions do
   @doc """
   Asserts that `value1` and `value2` differ by no more than `delta`.
 
+  This difference is inclusive, so the test will pass if the difference
+  and the `delta` are equal.
 
   ## Examples
 
       assert_in_delta 1.1, 1.5, 0.2
-      assert_in_delta 10, 15, 4
+      assert_in_delta 10, 15, 2
+      assert_in_delta 10, 15, 5
 
   """
   def assert_in_delta(value1, value2, delta, message \\ nil)
@@ -840,6 +843,9 @@ defmodule ExUnit.Assertions do
   @doc """
   Asserts `value1` and `value2` are not within `delta`.
 
+  This difference is exclusive, so the test will fail if the difference
+  and the delta are equal.
+
   If you supply `message`, information about the values will
   automatically be appended to it.