title: How to detect outlier detection in two dimensional arrays?
body: <p>Given an array like:</p>
  
  <pre><code>[ 
    { final_amount: 20.0, shipping_amount: 5 },
    { final_amount: 30.0, shipping_amount: 5.5 },
    { final_amount: 25.0, shipping_amount: 105.5 },
    { final_amount: 325.0, shipping_amount: 125.5 }
  ]
  </code></pre>
  
  <p>How could I detect that</p>
  
  <pre><code>  { final_amount: 25.0, shipping_amount: 105.5 }
  </code></pre>
  
  <p>is an outlier?</p>
  
  <p>Bigger final_amount means bigger shipping_amount, however we have some bad entries in our data set.</p>
  
  <p>If I take into consideration only shipping_amount (with median and standard deviation) it removes some valid entries because it's not taking the final_amount into consideration.</p>