title: How to calculate an average, skipping blanks
body: <p>I have a spreadsheet, where I keep the times I come in and leave at and from work.
  In the next column, I summarise those values in order to see the amount of time I spent at work, which gives me the amount of time I spent at work during a week.</p>
  
  <p>Now I'd like to know what is the average time I spent at work during a week.</p>
  
  <p>I'd thought I could achieve this using the <code>AVERAGEIF</code> function, using <code>"&gt;0"</code> in order to skip blank entries, but this seems not to work:</p>
  
  <p>E.g.</p>
  
  <pre><code>        A          B           C     D      E     F
  1       Day        Date        In    Out    Diff  Cumul
  2       Monday     13/10/2014  8:15  16:30  7:30  
  3       Tuesday    14/10/2014  8:15  17:10  8:10  
  4       Wednesday  15/10/2014  8:05  17:10  8:20  
  5       Thursday   16/10/2014  8:25  17:10  8:00  
  6       Friday     17/10/2014  8:25  17:00  7:50  
  7       Saturday   18/10/2014                     39:50
  </code></pre>
  
  <p>As you see, column E contains the difference between "In" and "Out" (taking into account the lunch break), column F contains the sum of the values of column E.</p>
  
  <p>For calculating the average of the entries in column F, I've tried to use the function "AVERAGEIF", as follows:</p>
  
  <pre><code>=AVERAGEIF(F1:F7;"&gt;0") // I thought of "&gt;0" for skipping blanks,
                         //  and so only use cells which are filled in.
  </code></pre>
  
  <p>The result of this function however is 15:50 (no idea how to interpret this), afterwards I'd like to replace "F1:F7" by "F:F" for calculating the average of the whole sheet.</p>
  
  <p>There are two solutions to my problem:</p>
  
  <ul>
  <li>either tell the <code>AVERAGEIF</code> formula only to use the cells F7, F14, F21, ... (is this even possible?)</li>
  <li>either keep on using the "F:F" range but use another condition than ">0" for skipping blanks, I think this is the easiest solution.</li>
  </ul>
  
  <p>Does anybody know how to skip blanks in formulas?</p>
  
  <p>Thanks</p>