title: Standard deviation in numpy
body: <p>Here is my code:</p>
  
  <pre><code>import numpy as np
  print(np.std(np.array([0,1])))
  </code></pre>
  
  <p>it produces <code>0.5</code></p>
  
  <p>I am confident that this is incorrect. What am I doing wrong?</p>