On randomization, modeling and experimental design: some remarks on a paper by De Vos

De Vos (1991) claims to have discovered a new example from agricultural field experimentation which shows that a simple robust spatial model may lead to inference and systematic experimental design that outperforms the inference from randomized experiments by far. In this reaction it is shown that: (1) the example is not new; (2) the gains in efficiency are exaggerated due to comparison with an inefficient randomization method; (3) the paper is over-optimistic with respect to robustness of model-based methods and throws unjustified doubts on the validity of randomization methods; (4) the choice between randomization methods and model-based methods depends on the relative importance attached to efficiency and validity.