Informant selection is highly relevant for ethnobotanical research, as people are constantly looked upon for knowledgeand information. The purposive sampling technique is a type of non-probability sampling that is most effective when one needs to study a certain cultural domain with knowledgeable experts within. Purposive sampling may also be used with both qualitative and quantitative researchtechniques. The inherent bias of the method contributesto its efficiency, and the method stays robust even when tested against random probability sampling. Choosingthe purposive sample is fundamental to the quality of data gathered; thus, reliability and competence of the informantmust be ensured.
Ma. Dolores C. Tongco (2007) studied this question.