When a study advertises recruitment efforts using QR codes, flyers, social media links, email campaigns, or other public survey links, potential participants may be able to access the same external survey more than once. This can increase the chance of duplicate survey submissions and duplicate potential participant records being created.
Survey Creator includes a setting that allows you to limit a survey to one response by assigning a unique cookie value. This can help reduce repeat submissions from the same browser.
About Duplicate Survey Submissions
Duplicate survey submissions occur when the same external survey is submitted multiple times by the same potential participant.
This may happen for several reasons. For example, a potential participant may not pass a prescreener and then retake the survey to try to qualify. In other cases, a potential participant may forget they already completed the prescreening form and submit it again.
Duplicate submissions can distort data analysis, inflate response metrics, and create duplicate potential participant records. Using tools to reduce multiple submissions helps support the accuracy and reliability of the data collected.
When to Use This Setting
The one-response cookie setting may be helpful when your study is sharing a public recruitment or prescreening survey through:
- QR codes on flyers
- Printed recruitment materials
- Social media posts
- Email campaigns
- Community outreach links
- Study landing pages
- Other publicly available survey links
This setting can help reduce the likelihood that the same person completes the same survey multiple times from the same browser or device.
How Cookies Help Prevent Multiple Submissions
Cookies store information in a user’s browser after the user submits a survey. This information indicates that the survey has already been submitted from that browser.
If the same person attempts to submit the survey again using the same browser, the presence of the cookie can help block the additional submission.
This allows the survey to be limited to one response from that browser without requiring the potential participant to complete additional verification steps.
How to Assign a Unique Cookie Value to a Survey
To help prevent repetitive survey submissions from the same browser:
- Open the survey in Survey Creator.
- At the top of the Property Grid, select Survey to switch to the survey-level settings.
- Under General, locate the field called Limit to one response.
- Enter a unique cookie value for the survey. This can be any text of your choosing.
- Save the survey.
Once saved, the survey will use the assigned cookie value to help identify whether the survey has already been submitted from that browser.
Important Limitations
Using cookies can help reduce duplicate survey submissions, but it may not prevent every duplicate.
Because cookies are stored in the user’s browser, a participant may still be able to submit the survey more than once if they:
- Delete cookies from their browser settings
- Disable cookies
- Use a different browser
- Use a different device
- Open the survey in private or incognito mode
- Enter different identifying information on separate submissions
For example, if a potential participant completes the survey multiple times but enters a different first name, last name, or date of birth, duplicate submissions may still appear.
However, if the potential participant enters the exact same first name, last name, and date of birth, using the cookie setting may help decrease the number of duplicate potential participant records created.
Best Practices
To help minimize duplicate survey submissions:
- Enable the one-response cookie setting for public recruitment or prescreening surveys.
- Use a unique cookie value for each survey.
- Include clear instructions asking participants to complete the survey only once.
- Require key identifying fields, such as first name, last name, and date of birth, when appropriate for your workflow.
- Review Potential Duplicates regularly in the Registry.
- Confirm duplicate records carefully before making updates or deleting participant profiles.
- Follow your organization’s data review and participant privacy policies.