Multiple (duplicated) studies & same completion code ! But also the same participants?

From the documentation I understood that one can use the same completion code for multiple/duplicated studies.
I see how this works, when participant 1, 2, 3 are doing the first study, and participant 4, 5, 6 do the second (duplicated) study.

However, I wonder, whether this still works, when the same participants (i.e., same ID’s) are invited to the following duplicated studies, hence they are not excluded.
I could imagine that there could be a conflict how Prolific handles the same participants coming back multiple times via the same link.

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Dear Simon

Welcome to the forum:-)

I did not know that the same completion code can be used for multiple studies. Thank you for letting me know.

I don’t think that completion codes are relevant to exclusion. Exclusion from studies is based upon participant ID and completion codes do not come into play.

If participants are aware that the completion code is going to be the same, then if you have not made the survey responses compulsary for proceeding through to the submission page (as I recommend that you do) then participants could, in theory, go to the last page and then submit the code that they already have. But, participants will not, in my experience do this, they won’t be aware what the codes are or that they are the same.

Ah, I see what you mean about the link. If it were only the link that determined what survey they are completing, then the prolific system would be confused as to which survey they are returning from. But fortunately it is not only the link. Participants can only do one study at a time so the system knows which study they are attempting. So the fact that the links are the same, (assuming they are), will not create conflict.



Hi Tim,

I was intrigued by this question, because the answer is not trivial and thought, surely I can add something :slight_smile:

But I have to say that your answer was clear and complete; nothing to add; well done.

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Hi Tim, Thanks for your reply!

This is great to hear that there is no conflict to be expected.