social desirability bias), second, depending on the type of intervention, sampling may be more complicated since villages or individual farms are often located in particular micro-climates, soil quality and access to ground water which are hard to detect and measure. In Rwanda, for instance, two apparently identical villages may be in separate valleys within just five kilometres distance, but subject to very different climate conditions. In the rural region around Cochabamba (Bolivia), soil quality at one side of the road may be very different than at the other side.

RCTs in practice

An ongoing 3ie funded study uses individual randomisation to examine the impact of a hybrid risk mitigation financial product that combines credit and insurance, called Risk Contingent Credit (RCC), in rural Kenya. 1,500 households were randomly assigned to receive one of three treatments – (1) the RCC, (2) traditional credit and (3) no credit. The randomisation was done through a public lottery at village level, and the villagers thus knew the treatment status of every participating individual.