<p>I agree that there is no universal <em>criterion</em>, which is why I am glad this question refers to the plural, <em>criteria.</em></p>
<h3>Negative Criteria</h3>
<p>If any of the following hold, the question likely does not need statistical expertise to understand or answer:</p>
<ul>
<li><p><strong>The only tag is for a <em>single</em> particular software platform</strong> (<em>e.g.</em>, <a href="https://stats.stackexchange.com/questions/tagged/r" class="post-tag" title="show questions tagged &#39;r&#39;" rel="tag">r</a>, <a href="https://stats.stackexchange.com/questions/tagged/excel" class="post-tag" title="show questions tagged &#39;excel&#39;" rel="tag">excel</a>, <a href="https://stats.stackexchange.com/questions/tagged/sas" class="post-tag" title="show questions tagged &#39;sas&#39;" rel="tag">sas</a>).  Examples:</p>
<p><a href="https://stats.stackexchange.com/questions/47199/multivariate-distance-function-in-excel">Multivariate distance function in Excel</a></p>
<p><a href="https://stats.stackexchange.com/questions/46817/how-to-find-sum-of-rows-that-contain-a-particular-substring-combination">https://stats.stackexchange.com/questions/46817/how-to-find-sum-of-rows-that-contain-a-particular-substring-combination</a></p>
<p><a href="https://stats.stackexchange.com/questions/48353/calculating-the-gini-coefficient-from-lis-data-in-stata">https://stats.stackexchange.com/questions/48353/calculating-the-gini-coefficient-from-lis-data-in-stata</a></p>
<p><a href="https://stats.stackexchange.com/questions/46848/how-can-i-determine-a-stata-files-ds-format-from-the-command-line">https://stats.stackexchange.com/questions/46848/how-can-i-determine-a-stata-files-ds-format-from-the-command-line</a></p>
<p><a href="https://stats.stackexchange.com/questions/46823/first-var-and-last-var-substitute-in-proc-sql">https://stats.stackexchange.com/questions/46823/first-var-and-last-var-substitute-in-proc-sql</a></p>
<p><a href="https://stats.stackexchange.com/questions/42963/implement-naive-bayes-and-oner-classifier-using-sas-enterprise-miner">https://stats.stackexchange.com/questions/42963/implement-naive-bayes-and-oner-classifier-using-sas-enterprise-miner</a></p>
<p>Something to notice about most of these examples is that their titles contain technical statistical terms.  The presence of such words does not imply the question itself is on topic!</p>
</li>
<li><p><strong>The question cannot (readily) be stated solely in English and mathematical notation:</strong> that is, it is specifically about code in a particular computing language and (typically) it cannot be understood except by somebody conversant with that language.  Example:</p>
<p><a href="https://stats.stackexchange.com/questions/47736/how-can-one-convert-multiple-dvs-from-long-to-wide">How can one convert multiple DVs from long to wide?</a></p>
<p>(This is also a good example of the &quot;routine data processing&quot; mentioned in the FAQ.)</p>
<p>Although there are many other examples, they are hard to find through any search mechanism.  Many of them are along the lines of &quot;my code doesn't work; please help me fix it....&quot;</p>
</li>
<li><p><strong>The question is purely mathematical.</strong>  Although it might possibly refer to a statistical application, it is unnecessary to know the application either to understand the question or to derive and describe an answer.  Examples:</p>
<p><a href="https://stats.stackexchange.com/questions/48460/simplifying-help-with-poisson-process-question">https://stats.stackexchange.com/questions/48460/simplifying-help-with-poisson-process-question</a></p>
<p><a href="https://stats.stackexchange.com/questions/47670/confusion-related-to-the-convexity-of-norms">https://stats.stackexchange.com/questions/47670/confusion-related-to-the-convexity-of-norms</a></p>
<p><a href="https://stats.stackexchange.com/questions/47359/confusion-related-to-calculation-of-hessian">https://stats.stackexchange.com/questions/47359/confusion-related-to-calculation-of-hessian</a></p>
</li>
</ul>
<p>I am <em>not</em> asserting that questions meeting any of these criteria automatically should be closed!  These are <em>flags</em> that should cause us to read the question carefully and consider whether the questioner and the community would be better served by migrating it, closing it, or--possibly--leaving it open.</p>
<h3>Positive Criteria</h3>
<p>There are too many to name.  Generally, questions that ask for interpretations, applications, and examples of things that are explicitly statistical or applied to data analysis tend not to be controversial, whether or not they are couched in a particular programming language or tied to a particular platform.  Our site currently has almost 15,000 such questions (out of 17,000 posted).</p>
<h3>On the Edge</h3>
<p>Finally, because it might help clarify the preceding, let me describe some characteristics of &quot;edge cases&quot;--those questions that might legitimately cause controversy and be difficult to place.  These might include</p>
<ul>
<li><p>Questions that otherwise would definitely be migrated but involve relationships among or interactions between specific statistical or data analysis software packages. It's possible the only people who could answer such questions are here and not on SO.</p>
</li>
<li><p>Questions about improving the utilization of computing resources for calculations with statistical and data-analytic applications.  Although these can be highly software-specific, they can have characteristics unique to statistical analysis and machine learning.</p>
</li>
<li><p>Questions that <em>look</em> like they belong elsewhere but for which there is some evidence the proposers have some underlying statistical concern.  These are questions like &quot;I wrote this code to perform ANOVA but it's failing with negative numbers because the logarithm is not defined for them&quot; (I paraphrase a recent question.)  The <em>programming</em> solution would be to trap the bad input, but--recognizing that no correct ANOVA algorithm is going to involve logarithms--the <em>statistical</em> solution might be to ask about the underlying ANOVA question.  The first solution would belong on SO (and the answers there would likely help the O.P. implement a working but horribly incorrect solution to their problem), but the statistical approach of eliciting a better question and then answering that would probably be much more helpful.</p>
</li>
<li><p>Questions that obviously overlap multiple sites, such as applying SDEs (finance might be a better place to get answers); about the roles of data analysts in academia (there's a site specifically devoted to such academic topics); or (hypothetically) about statistical terminology in non-English languages (there are sites specializing in French, German, etc. usage).</p>
</li>
</ul>
<hr />
<p>I invite readers to suggest additions or improvements to these criteria.</p>
