title: Understanding percentile= calculation in describes () of python
body: <p>I am trying to understand the following: 
  1)how the percentiles are calculated. 
  2) Why did python not return me the values in a sorted order (which was my expectation) as an output
  3) My requirement is to know actual value below which x% of population lies. How to do that?</p>
  
  <p>Thanks</p>
  
  <p>Python-2</p>
  
  <pre><code>new=pd.DataFrame({'a':range(10),'b':[60510,60053,54968,62269,91107,29812,45503,6460,62521,37128]})
  print new.describe(percentiles=[ 0,0.1 ,0.2,0.3,0.4, 0.50, 0.6,0.7,0.8 ,0.90,1 ])
  </code></pre>