Question Compare the statistical significance of the difference between two polynomial regressions in R is an obvious duplicate of question Comparing difference between two polynomial regression models in R (which is an exact duplicate of Comparing difference between two polynomial regression models in R). Now, as the new question is a duplicate of the other two, one should not answer it, right?

However, the user who posted the new question says that the two old questions have answers that are incomplete or unclear for him, given his level of knowledge of statistics. Question Comparing difference between two polynomial regression models in R effectively only has an answer which explains why not to use anova in this case (or better, not to naively use anova), but doesn't explain what to do (it suggests AIC, but I agree with the commenter to the answer that that's not the right thing to do). Question Comparing difference between two polynomial regression models in R has a first comment by user @Roland which in my opinion is great and answers the question correctly. However, it's a comment instead than an answer, and it would seem that the user who posted the new question doesn't understand it. I asked him what he doesn't understand exactly. What would be the right procedure to follow here? Flag the new question as a duplicate and add a more detailed answer, following @Roland's comment? Just flag the new question as a duplicate? Do something else?

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    $\begingroup$ The asker needs to explain what they learned from the duplicate & what they still need to know. Then we can provide the information they need without just duplicating the material from elsewhere that already didn't help them. $\endgroup$ Aug 22, 2016 at 12:05
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    $\begingroup$ A remark: we cannot normally close a Q as a duplicate of another Q that has no answers; only mods can perform such a closure. $\endgroup$
    – amoeba
    Aug 22, 2016 at 12:48
  • $\begingroup$ @amoeba you're right, I should have written more precisely "flag the question for closing as a duplicate" instead than "close". After writing the post I realised that it might be misinterpreted, but since I thought the intended meaning was clear from context, I didn't bother to edit. I will do it now. $\endgroup$
    – DeltaIV
    Aug 22, 2016 at 13:17

1 Answer 1


It is not uncommon to encounter a new question that is technically a duplicate of an older question, which however is for some reason unsatisfactory.

Maybe there are no answers at all; maybe there are some answers but they are all not good; maybe there is a decent answer there but the accepted answer is bad and OP left the forum so this will never change; maybe a correct answer is only in the comments; maybe the question itself is badly formulated, e.g. too detailed or too cumbersome.

All such cases should be considered individually, but one general rule is that one should not feel compelled to respect the older thread just because it is older.

Sometimes you may want to post a new answer in the old thread and close the new one as a duplicate. Sometimes you may want to post an answer in the new thread and close the old one as a duplicate of the new one. This should be decided based on what question is better formulated and/or has more chances to be more prominently seen. Sometimes you may want to ask and answer your own exemplary question and then to close both the new and the old questions as duplicates of your own one. Etc.

In this particular case two good answers have by now been posted in the new question and one of them is accepted; the question itself received several upvotes. Very well - so perhaps it would now make sense to close both older questions as duplicates. You can vote to close the oldest one. Once it gets closed you can flag the one that is already closed for moderator attention and explain there that it would be better to change the duplication target (to prevent "a duplicate of a duplicate" situation).

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    $\begingroup$ Ok, I will flag the oldest one for closure. Just to be sure, you are suggesting I flag it as a duplicate, right? I ask because in the "duplicate" option, it specifically states that the duplicate is a copy of an older question. In this case, it would be a (bad) copy of a newer question. I agree with your point of view that we don't need to respect the older thread just because it's older. I just want to be sure I'm clicking on the correct flag option. $\endgroup$
    – DeltaIV
    Sep 15, 2016 at 9:42
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    $\begingroup$ Yes. Indeed, it says This question has been asked before and already has an answer but I find this misleading, and I have voted to close multiple older questions as duplicates of newer questions and this never was a problem and has always (or at least mostly) been approved by the community and other voters. $\endgroup$
    – amoeba
    Sep 15, 2016 at 10:59

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