When testing a survey, you may share the survey with and gather input from participants who may not be applicable to your engagement effort. In these situations it's common to need to delete a person's responses to a survey.
To do this, navigate to your project page and click the Participants tab.
Search for the participant you're looking for and you'll notice a tiny "X" to the right of their name and location:
When you click this X, you'll be asked to confirm you'd like to delete this participant's responses for this project.
When you confirm, this person's responses to this project will be moved from the active data table to the archive, and their responses will no longer appear in reporting for this project or in the CRM.
Note that this will not prevent this participant from submitting future responses. To do this, it's best to wait until reporting time or survey closure to archive responses.
Please also note that deleted participant data and responses are stored for Federal Regulatory Compliance even as they are removed from project results & data.
Also: only Administrator-level may delete participant responses. Publishers and below will receive an error when trying to perform the function. Please see here for more info on permission levels.