title: Pandas get median/average of pre-aggregated data
body: <p>Assuming my data is already grouped how can I calculate median and other statistics?</p>
  
  <pre><code>Index  Value  Count
  0      6      2
  1      2      3
  2      9      8
  </code></pre>
  
  <p>In the example above I want to get the median/average etc of column Value taking into account the column 'Count'</p>
  
  <p>The actual values are 2,2,2,6,6,9,9,9,9,9,9,9,9 so my median would be 9.</p>