realized in declares realizable entity study design block design blocking variable restricted randomization restricted randomized design adapted from wikipedia Philippe Rocca-Serra a restricted randomized design is a kind of study design which uses randomization to allocate observation unit to treatment but where intuitively poor allocations of treatments to experimental units are avoided, while retaining the theoretical benefits of randomization. This is often the case when so-called 'hard to change' factors are used in an experimental design. ready for release