<p>I have long believed that organizing tags optimally will require some level of constant maintenance, and is one of the most important aspects of enhancing the usability of the site, and maintaining it more generally.  Personally, I tend to be in favor of merging tags more aggressively than seems to be the case, although I certainly agree it could go too far.  Basically, I think tags should be merged unless it is easy to think of questions (whether or not anyone has actually asked them yet) that clearly fall under one of the tags, but not the other.  Moreover, I don't mean terminological issues in the sense that something is called by one name in one discipline &amp; another name in a different discipline.  In such a case, the two tags should exist, but the lower-frequency variant should become a synonym for the higher-frequency variant.  That way, when someone searches on the name they know, something will show up, but it will be remapped to the standard version.  In the referenced discussion, for example, both @AndyW and @chl seem to agree that there isn't a substantive difference between the tags they are discussing, but that they do often connote different things to some people.  In a case like that, I say <em>merge</em>.  As a result of these considerations, I would argue that all 4 tags in suggestions 1 &amp; 2 should be merged into <code>mixed-model</code>, which is the most commonly used, and has a wiki excerpt that explains it is used for a bunch of different names for the same thing.  </p>

<p>I do think <code>glmm</code> and <code>random-effects-model</code> <em>could</em> stay, because I can imagine questions that fit better under them than mixed / multilevel etc.  Some examples could be questions about glmms vs. gee, or the referenced question about the interpretation of the meaning of the random intercept.  (For the record, I think <code>random-effect</code> would be better for this than <code>random-effects-model</code>.)  I acknowledge that these questions could go without these tags, and just have <code>mixed-model</code>, but I think something would be lost in a way that wouldn't occur if someone asked about students within classes within schools and clicked on the <code>multilevel-analysis</code> tag, but ended up with <code>mixed-model</code> instead.  </p>

<p>I don't have a strong sense of what should be done with the R tags (<code>lme</code>, &amp; <code>lmer</code>).  </p>

<p>I also strongly believe that <em>all tags should have wiki excerpts</em> at a minimum.  (I'm fairly indifferent to whether they have full tag wiki entries--I doubt anyone even reads them.)  I think that excerpts would best include a little about the topic, <em>and</em> a little guidance on the appropriate usage of the tag.  One thing to note is that the wiki excerpt give you a certain limit of characters, but not all of them will show up when possible tag matches are displayed on a question.  </p>

<p>I approve of your suggested excerpt for <code>random-effects-model</code>.  </p>
