<p>I don't see any necessary problem with asking a question like that.  Here are some things to be sure you do:  </p>

<ol>
<li>Provide a complete and correct citation for the paper.</li>
<li>Provide a link to the paper.</li>
<li>Paste into the body of your question the equation / text you need help understanding (i.e., don't just say 'I need help with equation 5').  </li>
<li>Paste in enough of the context that the question can stand on its own and potential answerers don't <em>need</em> to read the paper to answer your question, if they don't want to.  </li>
</ol>

<p>I recognize that the existence of <strong>4</strong> seems inconsistent with <strong>1</strong> and <strong>2</strong>, but you should do all four.  </p>

<p>N.B., you say that your question is statistical.  I have no reason not to take you at your word.  But if your question were only about, say, the <em>derivation</em> of the equation, 'how does equation $i$ fall out of equation $i-1$', it may be a better fit on SE's <a href="https://math.stackexchange.com/">math site</a>.  Likewise, if it were about the economic implications of the equation, it may be a better fit on SE's <a href="https://economics.stackexchange.com/">economics site</a>, etc.  </p>
