Surveys can be made to be 100% anonymous. This means that in Analytics, the responses would be shown; however, there’d be no way to correlate the responses with the respondents.
With anonymous surveys, all potentially identifying information about respondents is permanently hidden (email addresses, IPs, invite codes, referring URLs, etc).
This can be especially useful in cases where you want to encourage complete honesty, such as employee satisfaction or teacher evaluation surveys.
Here is a quick video tutorial on this topic: