Is it possible to give participants a choice between a longer and shorter version of a study?

My study will have 1 longer version and 1 shorter version. Is there a way to give participants the option to choose one of the two options (without them being able to complete both versions)? Or do I have to run 1 version of the study first, then a second version that excludes participants from the first version?

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Dear Dani

Welcome back :slight_smile:

There is no problem giving participants a choice of survey using branching in your survey tool or by using
if the survey’s are the same length but when they are of different
length a problem arises as to how much to pay the participants (with d i discussion on this somewhere on the forums but…)

However, recently with the implementation of custom completion codes, under the heading “Optional Custom Completion Codes” you can choose the option of “Earned a Bonus Payment” and then give that completion code to those participants who completed the longer version.

If you tell participants in advance, they will probably all chose the longer version . I think that it should (imho) be okay to warn participants in the description instead that there are different versions and that longer versions get a bonus, without telling them which is which.

I hope that works for you, and would love to know if it does.


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Dear Tim,

Thanks for that suggestion. I should have mentioned, though, that the 2 versions are of vastly different lengths: 1 survey may take ~30 min, while the other may be closer to an hour.

So, with the method you suggested, the bonus payment would be substantial and would need to be roughly equal to the original payment. It seems like this could have ramifications for Prolific’s calculation of study time and determination of whether participants are being compensated appropriately.

Also, given the length of the surveys and the fact that one survey is double the length of the other, I think I would have to be clear with participants about the two different options and the bonus payment.

But if everyone is likely to choose the longer version given the option, then it might make sense to just keep the studies separate and run the second study after the first has been completed.

Does that make sense? Please let me know if you have any additional thoughts.


Dear Dani

I am sorry I am so slow to respond.

With survey lengths of 30 minutes and one hour, you may find that participants elect to do the shorter of the two. Most surveys that I am aware of are shorter, and can be fitted into the gaps in the day, rather than having to be timetabled for as it were, which is likely in at least the case of the hour long study.

Now that there are automatic bonuses, i am not sure if the fair payment algorythms have been updated. If not then as you say, if the median time spent on the study were less than a fair wage for then it may result in extra fair-wage payments to the longer study participants.

Two separate studies would be the safer option.



Thanks so much, Tim! That makes sense and is helpful. I really appreciate your guidance.


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