Privacy refers to an individual person and to their interest in controlling others' access to themselves.
Confidentiality refers to data and to limiting the access to private data about a person.
Anonymity means that names and unique identifiers of subjects are never attached to the data, or known to the researcher. All research involving human subjects must limit access to private information about the subject unless the investigator has the permission of the subject to do otherwise. Even projects considered exempt from full protocol review must include assurance of confidentiality. Without assurance of confidentiality, potential participants may be unwilling to give honest answers about themselves. Researchers may be ordered by subpoena, or by other process of law, to disclose confidential information about a subject.