Informant consensus factor (ICF) was computed to measure the level of homogeneity of the information collected and overall agreement on the treatment of specific health disorder category and to identify potential medicinal plant species used for the traditional treatment of human disease categories in the two districts by using the method found in [18]. During information gathering, the informants were contacted three times for the same ideas to determine the reliability of information recorded during the first interview, and the information that was repeated in the same manner by the informants at three contact times was recorded as stated in [19]. ICF was computed as follows: ICF = Nur–Nt/(Nur–1), where Nur is the number of use reports from informants for a particular plant use category, Nt is the number of species that is used for that plant use category for all informants. ICF values range between 0 and 1, where “1” shows the highest level of informant consent [18].

The relative healing potential of each reported medicinal plant used against diseases was also tested using an index of fidelity level (FL), and it was calculated as follows: FL (%) = (Ip/Iu) × 100. Here, Ip is the number of informants who independently cited the importance of a species for treating a particular disease, and Iu is the total number of informants who reported the plant for any disease [19].

A preference ranking exercise was conducted to rank the medicinal plant that was the most preferred for a particular disease type. In this exercise, the medicinal plant which participants thought to be most effective in treating the reported diseases got the highest value, whereas the one with the least effectiveness got the lowest value (1) [17]. Based on the total score of each species, the rank was determined. This assisted in determining the most effective plant used by the community to treat the most commonly reported diseases.

A direct matrix ranking exercise was also used to test the use diversity of multipurpose medicinal plants of the sampled study areas, as stated in [20]. The exercise also aided in identifying which of the multipurpose plants is most under pressure in the area and to identify the factors which are the threats of medicinal plants. The participants in this exercise were selected based on their long years of experience as traditional herbal medicine practitioners [19] in the districts. For the exercise of direct matrix ranking, a focus group discussion (FGD) was conducted to know the preference based on multipurpose criteria on the plants.

The collected data were all documented to assess overall use values and diversity of species following [18]. All informants of the study were interviewed at the same time for the use diversity of medicinal plants following the method found in [17, 20]. The local importance of some representative medicinal plants was calculated by using the use value technique (UV). The use value was calculated using the formula UV = ∑Ui/n [18], where Ui is the number of uses mentioned by each informant for a species, and n is the total number of informants.

The significance of traditional knowledge difference (on the medicinal plants and the disease treated) between general and key informants, adults (≤50 years) and elders (>50 years), female and male, and illiterate (including church and elementary education) and literate was compared using a statistical test and one way ANOVA at 95% confidence level by using SPSS version 20 following the method used in [19].