<p>I want to agree with <a href="https://stats.meta.stackexchange.com/users/805/glen-b">Glen_b</a> here, but more emphatically.  Once a question has been asked and has received an answer, it is not appropriate for the OP to change the question.  That wastes the time of the person who answered, and gives the false impression that they did not answer the question correctly.  Once answers have come in, edits to the question should be limited to refining it to be clear; it is not appropriate to change the substance of the question in a way that renders existing answers defunct.  If the OP wishes to change the substance of the question then he/she should instead ask a new question.</p>

<p>I think the fairest thing here is to flag the inappropriate edits to the question and have moderators roll-back the edits so that the original question stands.  This could be augmented by a comment to the OP recommending that they ask a new question.  Although Glen gives some other possibilities in his answer, as second-best cases, I am of the view that the edits should be rolled-back.</p>
