I just had a quick question on making a survey on an external link as a HIT on Amazon Mechanical Turk. If a user completes the survey on the external webpage and submit the survey code on the MTurk interface, how do I, as the requester, guarantee that the user won't do the survey again? As in the user should only do the survey once. So is there a way to only allow the user to click on the survey link only once? Thank you!
Each worker is restricted to completing a HIT only once. Of course, if you setup your survey software to not log each worker's WorkerId, it is possible they might click the link multiple times before completing the HIT.
I recommend logging the WorkerId in your survey sytem. You can take a look at some instructions I've put together here for how to achieve this using JavaScript.