er">0</span></code>,
          since no sample can have a negative variance!
        </p>
<p>
          This procedure uses the method in Diamond, W. J. (1989). Practical Experiment
          Designs, Van-Nostrand Reinhold, New York.
        </p>
<p>
          See also section on Sample sizes required in <a href="http://www.itl.nist.gov/div898/handbook/prc/section2/prc232.htm" target="_top">the
          NIST Engineering Statistics Handbook, Section 7.2.3.2</a>.
        </p>
<h5>
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