Sampling problems in Brazilian research: a critical evaluation of studies on medicinal plants

This work compiled Brazilian articles regarding medicinal plant use by local communities in order to analyze the most common sampling problems and if research characteristics can influence the presence of sampling irregularities. We focused on studies about medicinal plants that present a species-indications list and had a quantitative nature. The proportion of works with and without sampling problems was evaluated considering the journal impact factor, period of publication, community status (urban x rural), sample type, presence of testing hypothesis and presence of research questions. We found that an alarming proportion of papers had some kind of sampling problems (48.39% serious and 19.35% moderate). The most common problems were related to: lack of information regarding the sample size or the universe, small sample sizes and selection of specialists based on obscure criteria. We could not find a significant influence between our tested variables and the occurrence of sampling problems, except for the community status (urban x rural). Results indicate that a significant amount of intracultural diversity is not properly captured, taking into consideration both the population as a whole and a group of interest in the community (= healers).