There are many different kinds of field research in which researchers can take any number of roles. Being a complete observer and using direct observation for research means studying a social process without becoming a part of it in any way. It is possible that, because of the researcher's low profile, the subjects of the study might not even realize that they are being studied. For example, if you were sitting at a bus stop and observing jaywalkers at a nearby intersection, people would likely not notice you watching them. Or if you were sitting on a bench at a local park observing the behavior of a group of young men playing hacky sack, they probably would not suspect you were studying them. Read more
about direct observation and when it is appropriate to use.