According to federal regulations, human subjects are defined as living human beings with whom an investigator obtains data through what methods?

The correct answer focuses on the methods by which data is obtained from living human subjects. Federal regulations, specifically those outlined by the Department of Health and Human Services (HHS) under 45 CFR 46, define human subjects as individuals from whom an investigator obtains data through interaction or intervention.

Interaction refers to direct communication or contact with the individuals participating in the research, which could include interviews, discussions, and surveys that yield personal or sensitive information. Intervention goes a step further, as it involves not only gathering data but also altering the study subjects' behavior or physical state through any kind of experimental procedure, treatment, or manipulation.

Both interaction and intervention are fundamental in research involving human subjects, as they establish the necessary engagement between the researcher and the participant that informs ethical guidelines and protocols for research. This ensures that the subjects' rights, dignity, and well-being are considered in the research process.

In contrast, other methods listed, such as surveys and analysis, observations, historical research, or social media interactions, may not directly involve the same level of engagement with subjects as defined under the regulations, and thus do not encapsulate the comprehensive requirements of obtaining data from living individuals as stipulated in federal regulations.