In convenience sampling, the selection of units from the population is based on easy availability and/or accessibility. The trade-off made for ease of sample obtention is the representativeness of the sample. If we want to survey tourists in a given geographic area, we may go to several of the major attractions since tourists are more likely to be found in these places. Obviously, we would include several different types of attractions, and perhaps go at different times of the day and/or week to reduce bias, but essentially the interviews conducted would have been determined by what was expedient, not by ensuring randomness. The likelihood of the sample being unrepresentative of the tourism population of the community would be quite high, since business and convention travellers are likely to be underrepresented, and – if the interview was conducted in English – non-English speaking tourists would have been eliminated.
Therefore, the major disadvantage of this technique is that we have no idea how representative the information collected about the sample is to the population as a whole. But the information could still provide some fairly significant insights, and be a good source of data in exploratory research.