To study interaction between prison guards and inmates, a sociologist lived at a prison for several months. Only the warden and a few other administrators knew he had not been convicted of a crime. This is an example of

participant observation

Explanation:

Participant observation: In psychology, sociology, & anthropology, the term "participant observation" is described as one of the research techniques which is distinguished as the tendency of a researcher or an experimenter to observe the interested participants or subjects in their natural environment as being one of the members in the specific population of interest.

In the question above, the given statement is an example of participant observation.

a factory opens that mass-produces light bulbs.

explanation:

not sure if that's an answer to your questions but this is an example! : )

answer; one person; monarch;