Text: The techniques include fieldwork, ethnography, observation, and participant observation and have in common that an observer is physically present at a site, stays at the site for a fairly long time, has flexibility in deciding what data to collect from whom and under what circumstances, and can organize the inquiry according to the meaning of events to the participants rather than having to decide beforehand
Entailment: Fieldwork and ethnography are techniques that require an observer physically present.
Contradiction: Fieldwork and ethnography don't require an observer physically present.