title: Merging two statistical result sets
body: <p>I have two sets of statistics generated from processing. The data from the processing can be a large amount of results so I would rather not have to store all of the data to recalculate the additional data later on. </p>
  
  <p>Say I have two sets of statistics that describe two different sessions of runs over a process.</p>
  
  <p>Each set contains </p>
  
  <pre><code>Statistics : { mean, median, standard deviation, runs on process} 
  </code></pre>
  
  <p>How would I merge the two's median, and standard deviation to get a combined summary of the two describing sets of statistics. </p>
  
  <p>Remember, I can't preserve both sets of data that the statistics are describing. </p>