title: Excel: Standard deviation, ignoring #NA and blanks in the range
body: <p>I want to calculate the standard deviation with STDDEV.P for a range, but I want to ignore #NA and blank cells.</p>
  <p>#NA and blanks should NOT be included in the calculation as 0.</p>
  <p>I've reached this solution for ignoring #NA:</p>
  <pre><code>=STDEV.P(IF(NOT(ISERROR(Trade!AI5:AI154));Trade!AI5:AI154))
  </code></pre>
  <p>How do I ignore blank cells as well?</p>