title: How to use Cognos report studio to change default Total() calculation
body: <p>I have a crosstab report that calculates for failure rates for my products ; it has two measures (PASSCOUNT, FAILCOUNT) and a calculation FAILRATE (FAILCOUNT/PASSCOUNT+FAILCOUNT)</p>
  
  <p>The report layout looks thusly:</p>
  
  <pre><code>                   OEM
                     MODEL
  TESTYEAR TESTMONTH PASSCOUNT FAILCOUNT FAILRATE
  </code></pre>
  
  <p>When I select the Total icon, it logically adds up each of the columns like so</p>
  
  <pre><code>2012 OCT 7547  697  0.08
       NOV 9570  373  0.04
       DEC 1879  107  0.05
  ------------------------
  Total   18996  1177 0.17
  </code></pre>
  
  <p>My user however wants TOTAL FAILRATE to be</p>
  
  <pre><code>TOTAL FAILCOUNT/(TOTAL PASSCOUNT+TOTAL FAILCOUNT) 
  </code></pre>
  
  <p>which translates to  </p>
  
  <pre><code>1177 / (18996+1177) = 0.058
  </code></pre>
  
  <p>How can I create this custom total in the report? I am reading about creating a Query calculation but I am not clear this is the right approach.</p>
  
  <p>Cognos Report Studio 8.4 IBM DB2 UDB</p>