<p>Recently a <a href="https://stats.stackexchange.com/questions/35231/how-to-interpret-a-random-intercept">question</a> came up that I felt had several redundant tags for variants of multilevel or mixed-effects models. As far as I can tell, there are six tags I can find that are related to this topic some of which have tag wikis and some do not (for whatever that's worth): </p>

<ul>
<li><a href="https://stats.stackexchange.com/questions/tagged/multilevel" class="post-tag" title="show questions tagged &#39;multilevel&#39;" rel="tag">multilevel</a> (no tag wiki)</li>
<li><a href="https://stats.stackexchange.com/questions/tagged/multilevel-analysis" class="post-tag" title="show questions tagged &#39;multilevel-analysis&#39;" rel="tag">multilevel-analysis</a> (has a tag wiki and has <a href="https://stats.stackexchange.com/questions/tagged/hierarchical-analysis" class="post-tag" title="show questions tagged &#39;hierarchical-analysis&#39;" rel="tag">hierarchical-analysis</a> as a synonym)</li>
<li><a href="https://stats.stackexchange.com/questions/tagged/mixed-model" class="post-tag" title="show questions tagged &#39;mixed-model&#39;" rel="tag">mixed-model</a> (informative tag wiki)</li>
<li><a href="https://stats.stackexchange.com/questions/tagged/mixed-effect" class="post-tag" title="show questions tagged &#39;mixed-effect&#39;" rel="tag">mixed-effect</a> (only four questions tagged, and oldest less than a month ago; no tag wiki)</li>
<li><a href="https://stats.stackexchange.com/questions/tagged/random-effects-model" class="post-tag" title="show questions tagged &#39;random-effects-model&#39;" rel="tag">random-effects-model</a> (no tag wiki)</li>
<li><a href="https://stats.stackexchange.com/questions/tagged/glmm" class="post-tag" title="show questions tagged &#39;glmm&#39;" rel="tag">glmm</a> (only four tagged questions, but has an informative wiki)</li>
</ul>

<p>There are also (at least) two related software tags:</p>

<ul>
<li><a href="https://stats.stackexchange.com/questions/tagged/lmer" class="post-tag" title="show questions tagged &#39;lmer&#39;" rel="tag">lmer</a> (informative tag wiki)</li>
<li><a href="https://stats.stackexchange.com/questions/tagged/lme" class="post-tag" title="show questions tagged &#39;lme&#39;" rel="tag">lme</a> (no tag wiki)</li>
</ul>

<p>This point <a href="https://stats.meta.stackexchange.com/questions/890/should-mixed-model-and-multilevel-analysis-be-tag-synonyms">has been discussed in a previous meta post by Andy W</a>, but it doesn't seem to have resolved everything; or, perhaps, new developments have arisen in the meantime. I realize there are methodological and semantic differences between some of these terms (as chl and Andy W discussed in the comments of that post), but it still seems like an awful lot of tags...! </p>

<p><strong>Suggestions</strong></p>

<ol>
<li>Questions tagged <a href="https://stats.stackexchange.com/questions/tagged/multilevel" class="post-tag" title="show questions tagged &#39;multilevel&#39;" rel="tag">multilevel</a>and <a href="https://stats.stackexchange.com/questions/tagged/multilevel-analysis" class="post-tag" title="show questions tagged &#39;multilevel-analysis&#39;" rel="tag">multilevel-analysis</a> should be merged.</li>
<li>Questions tagged <a href="https://stats.stackexchange.com/questions/tagged/mixed-model" class="post-tag" title="show questions tagged &#39;mixed-model&#39;" rel="tag">mixed-model</a> and <a href="https://stats.stackexchange.com/questions/tagged/mixed-effect" class="post-tag" title="show questions tagged &#39;mixed-effect&#39;" rel="tag">mixed-effect</a> should be together as well.</li>
<li>Questions tagged <a href="https://stats.stackexchange.com/questions/tagged/glmm" class="post-tag" title="show questions tagged &#39;glmm&#39;" rel="tag">glmm</a> could be merged into the appropriate one of those categories and then also given a <a href="https://stats.stackexchange.com/questions/tagged/generalized-linear-model" class="post-tag" title="show questions tagged &#39;generalized-linear-model&#39;" rel="tag">generalized-linear-model</a> tag? There are probably questions that are not marked as <a href="https://stats.stackexchange.com/questions/tagged/glmm" class="post-tag" title="show questions tagged &#39;glmm&#39;" rel="tag">glmm</a> that should be though...</li>
<li>The <a href="https://stats.stackexchange.com/questions/tagged/random-effects-model" class="post-tag" title="show questions tagged &#39;random-effects-model&#39;" rel="tag">random-effects-model</a> tag deserves a tag wiki. Unless someone else would contribute something more detailed, I would propose something like </li>
</ol>

<blockquote>
  <p>Parameters associated with the particular levels of a covariate are
  sometimes called the “effects” of the levels. If the levels that are
  observed represent a random sample from the set of all possible levels
  we call these effects "random."</p>
</blockquote>

<p>which is a paraphrase from <a href="http://lme4.r-forge.r-project.org/book/" rel="nofollow noreferrer">Douglas Bates' book</a>. (I think unpublished or in press at this point.)</p>
