Which of the following describes 'observational research'?

Observational research is characterized by the systematic observation of behavior without any interference from the researcher. This method allows for the collection of data in a natural setting, where behaviors can be recorded as they occur. By not intervening or interacting with the participants, the researcher can obtain genuine insights into the subjects' actions and interactions, thus reducing the potential for bias that might result from the researcher's presence. This type of research is often used in social sciences, psychology, and market research to understand how individuals behave in various environments or situations. It emphasizes objective data collection and often involves qualitative analysis, but can also include quantitative measures.

Other options describe different research methodologies that either involve direct interaction, computational methods, or rely solely on existing data, which do not align with the core principle of observational research.