title: Calculate the 3rd standard deviation for an array
body: <p>Say, I have an array:</p>
  
  <pre><code>import numpy as np
  
  x = np.array([0, 1, 2, 5, 6, 7, 8, 8, 8, 10, 29, 32, 45])
  </code></pre>
  
  <p>How can I calculate the 3rd standard deviation for it, so I could get the value of <code>+3sigma</code> as shown on the picture below?</p>
  
  <p><img src="https://i.stack.imgur.com/jH4Pp.png" alt="enter image description here"></p>
  
  <p>Typically, I use <code>std = np.std(x)</code>, but to be honest, I don't know if it returns the <code>1sigma</code> value or maybe <code>2sigma</code>, or whatever. I'll very grateful for you help. Thank you in advance.</p>