rate of correct decisions,
  non-erroneous cases</p></li>
<li><p>In terms of frequencies,
  <code><a href="acc.html">acc</a></code> is the ratio of
  <code><a href="dec_cor.html">dec_cor</a></code> (i.e., <code><a href="hi.html">hi</a> + <a href="cr.html">cr</a></code>)
  divided by <code><a href="N.html">N</a></code> (i.e.,
  <code><a href="hi.html">hi</a> + <a href="mi.html">mi</a></code> + <code><a href="fa.html">fa</a> + <a href="cr.html">cr</a></code>):</p>
<p><code>acc = dec_cor/N = (hi + cr)/(hi + mi