title: algorithm used to calculate 5 star ratings
body: <p>I need to calculate 5-star ratings like the one on Amazon website. I have done enough search to find what is the best algorithm, but I am not able to get a proper answer. For example, if these are the ratings</p>
  
  <pre><code>5 star - 252
  4 star - 124
  3 star - 40
  2 star - 29
  1 star - 33
  </code></pre>
  
  <p>totally 478 reviews  </p>
  
  <p>Amazon has calculated this to be  "4.1 out of 5 stars". Can anyone tell me how this figure is arrived at? I am not able to get this just by doing average.</p>