<p>If the question's on-topic here I most usually comment, adding a link to the cross-post &amp; asking the OP to decide which site they want the question on. I don't close it, partly because we don't have a relevant close reason,<sup>&dagger;</sup> partly because that makes for more work later if the OP removes the cross-post &amp; wants it re-opening here, but mostly because it seems to me a heavy-handed response to a minor transgression. Once the questions are linked the worst that can happen is that the OP neglects to delete one of them, &amp; other users make the informed choice to provide similar (or different) answers on both sites. The more important thing is to explain what the rule is so that the OP can abide by it in future.</p>

<p>Sometimes I just delete the question; if it's unanswered, has been here a while, &amp; if the cross-post already has an answer. Rarely I suggest splitting it or tailoring it into two questions, each more suited for one or the other site.</p>

<p>There are so many SE sites now, &amp; so much overlap, that it doesn't seem worthwhile to spend time researching whether the question's on-topic both here &amp; on the site of the cross-post&mdash; though if I do happen to know enough to have an opinion on the most appropriate site I might share it. (I believe Mathematical Statistics is on-topic at the Maths site, for what it's worth.)</p>

<p>Deliberately &amp; persistently flouting the rules is another matter, of course.</p>

<p>&dagger; There's an "Other" close reason, as @gung suggests using, but the boilerplate reads </p>

<blockquote>
  <p>This question does not appear to be about statistics within the scope defined in the help center.
  If this question can be reworded to fit the rules in the help center, please edit the question.</p>
</blockquote>

<p>, which comes across a bit oddly. And what do you do if the question already has an answer?</p>
