ksemmler wrote: I am wondering how to get around to conduct follow-up studies if we develop a token based survey. If we set the second survey anonymous, can we still connect the data collected to the respondent to make a second study based on the responses of the first one?

If you do this : it's not anonymous …

As Denis says, if you could pass some kind of code in the invitation to connect survey 1 with survey 2 you have breached the "technical annoymity", because you are able to connect persona data (the email) with response data.

There are some ideas that technically would allow you to do what you are trying to do, but in practice I think they won't work.

E.g. you could create a code for each respondent in survey 1 and present it to them at the end and tell them to store /save it somewhere for the second survey. But you know that a lot of people will not find the code or will not even bother to search for the code anyway, so in theory this could allow you to connect the two response tables without connecting it to personal data. But in practice it won't work.

Maybe you could allow them to create a codeword themselves that is stored in survey one and then they need to put it also in survey 2. The chance that they remember it is probably slightly higher than for a random code, but it is probably more difficult to match later and there is a certain risk that the same codeword appears more than once in the first survey. So also not a good solution.

If you need to connect responses from survey 1 with survey 2, I don't see much alternatives than to "break" technical annonymity and promise to analyze anonymously.