title: Calculating the standard deviation from columns of values and frequencies in Power BI
body: <p>I am trying to calculate the standard deviation of a set of values in PowerBI and I am stuck. There are two columns in a table (days and count).  This is a frequency distribution of a transportation lane. Days goes from 1 to 100, count is the number of shipments that took those number of days.  </p>
  
  <p>The formula to calculate the standard deviation of a frequency distribution is pretty straight forward: sqrt(sum(fx * (x - avgx)^2))/sum(fx))  But the Dax is giving me a massive headache.  Any help would be much appreciated.  Thanks.</p>