Assign each item from a CSV exactly ONCE across participants

Question

Hi all,I have a Qualtrics survey connected to Prolific. I have a CSV/list of 90 unique writing prompts, and I need each prompt to be completed exactly once across the full study. So it is kind of in loop and merge land, but not quite. The important constraint is that this should not be simple randomization. I do not want participants randomly assigned to prompts, because that could create duplicates or leave some prompts unused. Ideally, I want participant 1 to receive one unused prompt, participant 2 to receive another unused prompt, and so on, until all 90 prompts have been assigned/completed once.My current understanding is that the built-in Qualtrics Randomizer or Loop & Merge randomization can balance presentation, but does not truly function as an inventory/assignment system that locks a prompt once it has been assigned, especially with concurrent participants or partial completions.Has anyone implemented this kind of “assign each row exactly once” workflow in Qualtrics?

Lpena · Answer

That’s a really interesting use case, but implementing a strict "inventory/assignment" system where each CSV row is guaranteed to be shown exactly once across concurrent participants is tricky. Because Qualtrics generally increments quotas and logic upon survey submission, concurrent sessions can run into race conditions where two participants pull the same item before either submits.

Standard A/B testing and randomizers handle branching nicely, but they don't guarantee that "row N goes to participant N" uniqueness. If you already have your participant list, the safest workaround is usually assigning the rows outside the survey beforehand. For instance, you could pre-assign blocks or variants directly into a contact list using an embedded data field before sending out your invites.

To give you the best advice on the exact logic to use, could you let us know if you have explicit identifiers for your Prolific participants ahead of time, and if pre-generating an assignment list is an option for your setup?

If this is holding up your project launch or you need someone to take a closer look at your specific survey flow, it might be worth dropping a line to the folks over at the Customer Success Hub. They can log into your account securely and help you map out a watertight workaround for concurrent sessions. Let us know how it goes! 😊

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