<p>I believe the <a href="https://stats.stackexchange.com/questions/tagged/multiple-regression">multiple-regression</a> tag has a purpose, because there is a clear distinction maintained in textbooks and people's minds between "simple" regression models and "multiple" regression models.  A regression problem becomes overtly "multiple" when one has to grapple with the mutual relationships among the independent variables.  To clarify this, I have created a wiki entry for <code>multiple-regression</code> to this effect.  As always, your suggestions about improving that are welcome.</p>

<p>It is likely that the distinction I am highlighting has not consistently been maintained by previous users of the <code>multiple-regression</code> tag.  The fix is to retag such questions whenever you run across them.</p>

<p>Alternatively, one could argue that the combination of the <code>multivariate</code> and <code>regression</code> tags achieves what my <code>multiple-regression</code> proposal does.  I think such an argument is valid and am interested to hear what people find more useful or natural.</p>
