<p>The tag's definition of the Hauck-Donner effect appears to be different than the classical one. To my knowledge, Hauck-Donner effect refers to an erratic behaviour (non-monotonicity) of the power of the Wald test, which is unrelated to the separability issue. As the following four citations show:</p>

<ol>
<li><p>A common interpretation of Hauck Donner effect is about power of Wald test</p></li>
<li><p>None of these papers (seems to) mention separability</p></li>
<li><p>Three next references show the presence of the Hauck Donner effect in other settings than the logit (such as GLM or ANOVA).  </p>

<ul>
<li><p>Original paper: Hauck, Donner (1977) Wald's Test as Applied to Hypotheses in Logit Analysis, Journal of the American Statistical Association, Vol. 72, No. 360</p>

<blockquote>
  <p>For tests of a single parameter in the binomial logit model, Wald's
  test is shown to behave in an aberrant manner.</p>
</blockquote></li>
<li><p>Vaeth (1985) <em>On the Use of Wald's Test in Exponential Families:</em></p>

<blockquote>
  <p>Hauck &amp; Donner (1977) showed that Wald's test (the maximum likelihood
  test statistic) behaves in an aberrant manner when applied to
  hypotheses about a single parameter in a binomial logit model. [...] Finally, the use of Wald's test in the analysis of generalized linear models is discussed.</p>
</blockquote></li>
<li><p>Mantel (1987) <em>Understanding Wald's Test for Exponential Families:</em></p>

<blockquote>
  <p>[...] demonstration by Hauck and Donner (1977) that in certain
  multiparameter situations in which interest focuses on one of several
  parameters, Wald's test statistic (the maximum likelihood test
  statistic) can decrease to 0.</p>
</blockquote></li>
<li><p>Fears et al (1996) A Reminder of the Fallibility of the Wald Statistic</p>

<blockquote>
  <p>Hauck and Donner and Vaeth have identified situations in which the
  Wald statistic has poor power. We consider another example that is not in the classes discussed by those authors. We present data from a balanced
  one-way random effects analysis of variance (ANOVA) that illustrate the poor power of the Wald statistic.</p>
</blockquote></li>
<li><p>Venables and Ripley (2002, p. 198) <em>Modern Applied Stats with S</em>, give a similar definition of Hauck and Donner. Interestingly, they mention Hauck Donner and separation together: </p>

<blockquote>
  <p>There is one fairly common circumstance in which both convergence problems and the Hauck–Donner phenomenon can occur. This is when the fitted probabilities are extremely close to zero or one.</p>
</blockquote></li>
</ul></li>
</ol>

<p>Now it needs to be shown that the tag's definition of Hauck Donner effect is also an accepted one? What are the references for that one? In absence of sources, a deeper cleaning of the tags might be required?</p>
