We applied a three-stage random sampling design to select 1,200 respondents. In the first stage, we randomly selected 60 villages, 30 villages in Yogyakarta and 30 villages in Tasikmalaya. In the second stage, we randomly drew farmer group(s) in selected villages. Farmer groups in Indonesia function both as social group but also as task groups for government programmes and the allocation of subsidies.
In each village, we selected a minimum of one and a maximum of three farmer groups until the total number of registered farmer group members from the selected groups was equal to or larger than 60. We set the minimum to 60 members to ensure that a sufficient number of farmers would attend our information sessions (assuming that only a fraction of the members is interested) from which we drew our study participants. After identifying the farmer groups, the members of the selected farmer groups were invited to an information session on organic farming, which was held in their village. These information sessions served two purposes: (1) to facilitate self-selection based on initial interest in organic farming and the willingness to participate in farmer group events; and (2) to collect contact details on prospective respondents. The information sessions were run by AOI. In the third sampling stage, we randomly drew 20 farmers among the attendees of each information session. These 1,200 farmers, 20 from each of the 60 villages, constituted the respondents of our survey. If there were fewer than 20 attendees at the information session, we asked the farmer group head to nominate additional farmer group members.
The treatment was randomised at the village level and consisted of training on organic farming methods and principles. Farmers from groups in control villages did not receive any training. As baseline data was not available at the time of the randomisation, we used publicly available regional data for the stratification. Specifically, we stratified the sample according to urban and rural status and the reported size of agricultural land area per village. In Tasikmalaya, we used ‘travel distance to the district capital’ as an additional stratification criterion as this region is characterised by less developed infrastructure.