formation (i.e., function to square a number).</p></li>
<li><p><code>transf.irft</code>: Freeman-Tukey transformation for incidence rates. See Freeman and Tukey (1950). The <code>xi</code> argument is used to specify the incidence rates and the <code>ti</code> argument the corresponding person-times at risk.</p></li>
<li><p><code>transf.iirft</code>: inverse of the former.</p></li>
<li><p><code>transf.ahw</code>: transformation of coefficient alpha as suggested by Hakstian and Whalen (1976), except that <em