never be exactly repeated. These
range from the relatively mundane (a researcher may not have the time
or funding to repeat a piece of research) to more serious
problems such as the fact that a group may break-up after a piece of
research has been completed or, more-significant perhaps, the
composition of the group being studied changes over time (which may mean
that a repeated piece of research would not be studying the same people
under the same circumstances).
For these reasons, participant observation rarely, if ever, aims to make generalisations about people's behaviour on the basis of the study of a relatively small (and probably unrepresentative) group.