The Odisha team has randomised at the village level while the Karnataka team is randomising at the Gram Panchayat (the village council, which is the lowest administrative unit in rural areas). The projects have chosen to randomise at different levels given differences in distance.

The previous examples have all been designed to respond to the question ‘does the programme work’ by having control groups that do not receive it. Quite often, however, what you want to test out is modifications to an existing programme to see whether adding a design component leads to improved effectiveness or by comparing different additions to judge which is the more effective innovation. This was the background for a 3ie-funded ongoing multi-arm RCT to test innovative modules of farmer extension services and their effect on agricultural productivity in Cambodia, within the Project for Agricultural Development and Economic Empowerment (PADEE). The authors investigate the impact of two additional features to the traditional extension worker model that provide agricultural advice.