Anonymous vs. Confidential
In research, the terms "anonymous" and "confidential" are often confused and treated as interchangeable. They have, however, very distinct meanings, and it is important for an investigator to understand the difference when developing his/her research study.
When conducting human subjects research, the level of risk to which subjects are exposed is an important consideration that the Institutional Review Board must determine in the course of its review. It is the investigator's responsibility to minimize the potential for harm to his/her research subjects.
The distinction between anonymous and confidential data relates to this level of risk to subjects, and the investigator must clearly define the activity as anonymous or confidential prior to conducting the research.
No activity can ever be both anonymous and confidential (though, a single research study may utilize numerous activities, or methods of data collection, some of which yield anonymous data and some of which yield confidential data).