I want to assure the respondents that the survey is anonymous.
We normally add text to the beginning of surveys that tell the respondents that their responses are anonymous. Some examples:
Participating in this survey is completely voluntary and AAAA anticipates very few risks from your participation. There is a small chance that you will feel uncomfortable with a question and not want to respond. Please remember that you do not have to answer any questions that you do not want to answer. Project staff will not share personal information from your survey responses with anyone outside this project. We will take every precaution to ensure your privacy. Participation in this survey will not affect your status with ZZZZ.
Responses for individual sites or respondents will not be identified in any study reports or publications. Although survey responses will be identifiable to QQQQ, the responses will not be used for compliance or monitoring activities.
The survey will take about 10 minutes to complete and your responses are anonymous. Thank you for taking the time to provide your feedback by October 30th.
Technically, there is not much that you can do. You can make your link secure, and you can go into TOOLS > RESPONSE OPTIONS and chose to hide location information, but I am not sure if that would mean anything to your respondents. You are going to have to rely on your credibility and then followup and make sure that the responses do remain anonymous.