title: Standard Deviation in R Seems to be Returning the Wrong Answer - Am I Doing Something Wrong?
body: <p>A simple example of calculating standard dev:</p>
  
  <pre><code>d &lt;- c(2,4,4,4,5,5,7,9)
  sd(d)
  </code></pre>
  
  <p>yields    </p>
  
  <pre><code>[1] 2.13809
  </code></pre>
  
  <p>but when <a href="http://en.wikipedia.org/wiki/Standard_deviation" rel="noreferrer">done by hand</a>, the answer is 2. What am I missing here?</p>