added definition "dof"

Author: JoramSoch

D/dof.md

@@ -0,0 +1,42 @@
+---
+layout: definition
+mathjax: true
+
+author: "Joram Soch"
+affiliation: "BCCN Berlin"
+e_mail: "joram.soch@bccn-berlin.de"
+date: 2024-10-11 11:55:01
+
+title: "Degrees of freedom"
+chapter: "General Theorems"
+section: "Probability theory"
+topic: "Probability distributions"
+definition: "Degrees of freedom"
+
+sources:
+  - authors: "Wikipedia"
+    year: 2024
+    title: "Degrees of freedom (statistics)"
+    in: "Wikipedia, the free encyclopedia"
+    pages: "retrieved on 2024-10-11"
+    url: "https://en.wikipedia.org/wiki/Degrees_of_freedom_(statistics)"
+  - authors: "Animated Software"
+    year: 2024
+    title: "Degrees of Freedom"
+    in: "Glossary of Statistical Terms"
+    pages: "retrieved on 2024-10-11"
+    url: "https://www.animatedsoftware.com/statglos/sgdegree.htm"
+
+def_id: "D206"
+shortcut: "dof"
+username: "JoramSoch"
+---
+
+
+**Definition:** Degrees of freedom can refer to
+
+* a [parameter](/D/para) or [parameters](/D/para) of certain [probability distributions](/D/dist), such as the [chi-squared distribution](/D/chi2), the [t-distribution](/D/t) or the [F-distribution](/D/f);
+
+* the number of values in the final calculation of a [statistic](/D/stat) that are free to vary, such as $n-1$ for a [sample variance](/D/var-samp) calculated from $n$ [data points](/D/data).
+
+Some [statistics](/D/stat) have [sampling distributions](/D/dist-samp) whose [parameters](/D/para) (in the former sense) are equal to their degrees of freedom (in the latter sense). For example, [a function of the sample variance follows a chi-squared distribution with $n-1$ degrees of freedom](/P/norm-chi2).