Longitudinal or multi-part studies

Create the first study

Create your initial study for the first time-point. This study should have:

• A clear description explaining the full structure of your study, especially if payment is contingent upon participation in follow-up stages
• Reward and estimated completion time that reflect only this stage of the study

Make a note of the study id from the response as you will need this in the following steps.

Publish the first study

Publish the study to start recruiting participants.

Once the study has successfully published, the study’s status will be ACTIVE. Wait for participants to complete the study before proceeding to the next step.

Get participant IDs from the first study

Once participants have completed the first study, you need to retrieve their participant IDs to create a custom allowlist for your follow-up studies.

If your survey software supports recording participant IDs from a URL parameter, you can collect participant IDs directly during the first study. Make sure to include the PROLIFIC_PID URL parameter in your study url to capture this information. You can find more information on using URL parameters in the URL parameters guide.

You can also get your participant IDs by getting the submissions for your study.

From the response, extract the participant_id from each submission you would like for your follow up studies.

You can also export the demographic data which includes participant IDs:

Next make a note of all the participant IDs as you will need them to create a custom allowlist for your follow-up studies. A custom allowlist ensures only participants who completed the first study are eligible for subsequent parts.

Create follow-up studies with custom allowlist

For each subsequent time-point, create a new study. Each follow-up study should:

• Have reward and estimated completion time that reflect only that stage of the study
• Use a custom allowlist filter to ensure only participants from the first study are eligible
• Include a clear description explaining it’s part of a longitudinal study

To use a custom allowlist, include a filter with filter_id set to custom_allowlist and selected_values containing the array of participant IDs you collected from the first study.

Multiple conditions: If you have multiple conditions and want to keep these conditions consistent between studies, you will need to set up a separate follow-up study for each condition and add only those participants you want to be eligible to each study’s custom allowlist. However, you will only need to run one study for the first part if your survey software supports allocation to conditions from one URL.

Make a note of each follow-up study id as you will need them to monitor and approve submissions.

Publish follow-up studies

Publish each follow-up study when you’re ready to collect data for that time-point.

You can publish all follow-up studies at once, or publish them at different times depending on your study design. If you want your participants to complete the follow-up studies at particular times, make sure to specify this clearly in your study description, including the time zone(s).

Monitor study progress

Check the status of your studies to see how many participants have completed each part.

You can also check submission counts for each study:

Review and approve submissions

Once participants have completed all parts of your longitudinal study, you can review and approve their submissions. You can get submissions for each study:

Payment timing: If your study consists of multiple waves within 21 days, you can wait until the final wave is complete before paying each wave. To do this, leave the submissions from the earlier studies as ‘awaiting review’ until you are ready to approve them. Submissions will be automatically approved after 21 days if they are still awaiting review at this point.

If the waves are over a longer period, all participants from each stage will need to be approved within 21 days.

To approve a submission, use the submission id and transition it to APPROVED:

You can find more information on reviewing submissions in the submissions guide.