<p><strong>Yes, that's the right way to view it:</strong> questions are migrated to sites where they are (a) on topic and (b) likeliest to get a great answer in a timely fashion.  Sometimes, as in this case, the very act of migration gives a clue as to how the question can be answered!</p>

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<p>Your moderators frequently have to field questions of mathematical statistics, or other theoretical questions, that ultimately have purely mathematical answers. My philosophy as a moderator is to keep the question here if it or any of its answers can be construed as having some statistical interest (such as in using statistical thinking to motivate a particular line of attack).  If the question otherwise is (for example) purely one about how to perform a particular mathematical manipulation, such as (in this case) how to apply the Chain Rule or (as in other common cases) how to apply optimization software, then migration seems the best course of action.</p>
