title: How to choose the OKAPI BM25 parameters : b and k1
body: <p>I was actually wondering, how can we validate or evaluate empirically the values of b and k1 in the BM25 formulas? in other terms what is the most 'scientific' way to evaluate it?</p>
  
  <p>Is there any research paper that we can refer to in order to see how this types of evaluations is done?</p>