Designing experiments with complex blocking and network structures

Vasiliki Koutra (King's College London, UK)

In this talk we propose a new method of constructing efficient designs with complex blocking structures and network effects, and we illustrate it using an agricultural field experiment. The idea is to view the potential interference among plots that can result from the spatial structure or farmer operations as a network structure. We consider a field trial running at Rothamsted Research and we obtain different designs accounting for the neighbour effects using an interchange algorithm. We provide a comparison of various optimal designs under different models, including the commonly used designs in such situations. We show that designs that ignore the neighbour structure perform poorly and their use can lead to imprecise estimates of the differences between treatment effects.