How to prevent multiple responses from the same participant using their ID number? | XM Community

How to prevent multiple responses from the same participant using their ID number?

  • 25 January 2019
  • 8 replies

I have three surveys that must be completed in order, with spacing of several weeks in between. I am surveying students, and want to ensure they can only complete each survey once. Prevent ballotbox stuffing won't work as they can use different computers to get around this. I think the easiest solution would be to ask for their student ID number at the start of the survey, and then do a validation check which involves checking if this number has already been entered in the recorded data, if it has, then they cannot proceed.

Is it possible to validate a response based on identical matches already submitted for that variable? I can't seem to find a way to do this.

Any help would be much appreciated

Best answer by Anonymous 25 January 2019, 19:22

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8 replies

Hello @Bluesk ,

Yes your understanding is correct to ask the student ID, but we need to store the survey complete flag in the contact list.

So once the student completes the survey, update the complete flag in the contact list using contact list trigger for the respective student ID.

Use authenticator to check the "complete flag" and based on status of the flag terminate or continue the survey
Thanks, I've set up the contact list, but I can't see how you can use the authenticator to check a complete flag. It seems to only check a contact list for an email address or external reference (studentID), but I want to stop respondents completing the survey more than once using their studentID. I don't know which students will complete the survey, so I need the authenticator to check an inputted studentID against a contact list, if there is a match, skip to the end of the survey, and if there isn't a match, skip to the question block. In this question block, once they have completed the final question I have a trigger to add the respondent to the contact list. So, for first respondents, they fail authentication and skip to questions, then are added to the contact list. If they attempt to repeat the survey, they will 'pass' authentication (because their student ID will be in the contacts list) and skip to the end of the survey.
It doesn't seem to allow this, as failing authentication leads to an error message being displayed, rather then simply continuing to a non-authenticated block.
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Badge +11

Hi Bluesk
did you find a solution for your inquiry above? I am facing the same issue.

Hi @Muqaibil

Yes - the Qualtrics support helped me out. It can be done using the authenticator and a contact trigger list but it's counter-intuitive: you have to set the survey flow so that failing the authentication means you get access to the survey (i.e. ID number entered in the authenticator doesn't appear in the trigger list, so they have done the survey before, therefore they get access to the survey), and passing the authentication (i.e. the ID entered does appear on the trigger list) takes you to a message telling the participant that their ID appears to have already taken the survey. If you contact support they can make a short video for you explaining the process. They did it for me, but unfortunately the link has expired so it's not available anymore. Here is their reply to me:

Thank you for contacting Qualtrics Support! After investigating, I was able to come up with a workaround solution for using authenticators to prevent respondents from taking the survey more than once.

It is important to note that, on the respondent's first time taking the survey, we want them to fail the authenticator to skip past the end of survey element and on to the survey. On the second time taking the survey, they pass the authenticator, so they are taken to the end of survey element.

You can customize the message that respondents see when they fail the authenticator. For instance, you could write a message along the lines of "It looks like you have not registered yet, please click next to register."

More information on authenticators can be found at, and more information on contact list triggers can be found at Please let me know if you have any other questions!
Userlevel 3
Badge +11
Thanks @Bluesk i will do so..

However, I solved this using another workaround (worked for a known list of IDs). I am posting that so it might be helpful for others to follow..

I set the authentication to be for External Data Reference where I put all the IDs in that field (required a dummy email addresses to fulfill Contact List creation process). Secondly, I created an additional field in the contact list (name it as 'Indicator" for example) and set the default value for it to be 'False'

In Survey Flow, I created an Embedded Data field as same as the one which was created in contact list. Afterward, I set the value to be 'True' and updating Contact List Trigger for the same filed after survey completion.

after authentication passed ( External Data Reference), I created a branch logic to check the value of the contact list. if the value is 'True' that means he/she did the survey and should be promoted to the end of survey otherwise the value is 'False' so he/she will be directed to the questions.

Below screen shots might be helpful for future usage for anyone..




I hope that would be supportive and helpful for the community 😊

Best Regards,
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Hi Muqaibil
I'm just here to say thanks for your idea. It's very helpful!
But I also hope Qualtrics understand people can create the same ID (contents) over and over with contact list trigger, it is so annoying to remove duplicate ID one by one.

Userlevel 3
Badge +11 a lot adafung and appreciate your comment...
In fact, if you would like to create your contact list based on contact list trigger, then you might need to have another survey and workaround for allowing only unregistered IDs to be updated to the contact list and then redirect them to the original survey which you use to collect responses through. They will be only authenticated against the contact list which was updated...

simply, its a registration form survey to create a contact list and authenticate another survey against that created contact list.. I hope its clear (although i dont think so 🙂

I think Qualtrics might think of having a better authentication system for the surveys and consider 2-step AUTH for all areas taking into account OTP approach for example as its always recommended security-wise...

Best Regards,

Badge +1

Muqaibil Thank you very much for your detailed and clear explanation. It is very helpful and understandable. 🙂 And yes, a separated registration form is a great idea if the participants need to go through multiple surveys later. I think I should do this for my project too.
Anyway, It is good to know they may have a better authentication system in the future. Hope it will be easier for everyone.

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