From 2df8d2c90a9ca7930552754e1327933d69d9350c Mon Sep 17 00:00:00 2001
From: Frank Sauerburger <frank@sauerburger.com>
Date: Thu, 19 Jul 2018 13:05:24 +0200
Subject: [PATCH] Add comment about -1 in dof

---
 README.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/README.md b/README.md
index 23d3923..7f94108 100644
--- a/README.md
+++ b/README.md
@@ -597,6 +597,12 @@ print("  p-value = %g" % p)
 
 ```
 
+The additional `-1` stems from the fact that we have a Poisson distribution
+for which the uncertainties are derived from the number of events. The
+test is not sensitive to the normalization, and therefore, we loose one degree
+of freedom, cf. [Data Analysis in High Energy
+Physics](https://www.wiley.com/en-us/Data+Analysis+in+High+Energy+Physics%3A+A+Practical+Guide+to+Statistical+Methods-p-9783527410583) by Behnke et at.
+
 If you run the `decay.py` you should see the following fit results.
 <!-- console_output -->
 ```bash
-- 
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