endl</span><span class="special">;</span>
<span class="comment">// 95% of area has a z between 1.95996 and -1.95996</span>
</pre>
<p>
            First, define a table of significance levels: these are the probabilities
            that the true occurrence frequency lies outside the calculated interval.
          </p>
<p>
            It is convenient to have an alpha level for the probability that z lies
            outside just one standard deviation. This will not be some nice neat
            number like