A public institution wanted to measure the health of its employees and designed a detailed survey with questions about their experience at work, mental load and satisfaction. The survey participants were guaranteed anonymity. Many employees took advantage of the offer and experienced an unpleasant surprise when their supervisor asked them about specific answers they had given in the survey. What happened?

The survey did not ask for names, but it did ask for a lot of detailed information and demographic data. Participants' responses were then analyzed and reported in such small groups/organizational units that derivable characteristics such as gender and job function made it possible to accurately match individuals to their responses. Thus, the promised anonymity was not maintained and many complaints were made to the responsible data protection officer, not to mention awkward conversations with the respective managers.

Particularly when evaluating small samples, attention must be paid to "derivable" personal data. Even if the name is not recorded, a combination of different data can make a person identifiable to others. In this case, the survey is no longer anonymous and the EU Data Protection Regulation must be observed - which requires, among other things, different declarations of consent and processing steps/technical and organizational measures than anonymous data.