The relative value of communication and observation

Communication methods are useful for gathering information from subjects who are difficult to reach, however, these answers can be sought in question one of this chapter. Observation is a good complement to communication; observation forms a good “cross-triangulation” device for cross-validation. For example, people in a particular neighnbourhood can be interviewed to attain their eating habits; data can be cross-checked with reviewing their garbage to see tins and boxes from food material.