ABSTRACT
We have emphasized that the validity of a randomization test rests on the way rearrangements of the data carried out in the test reflect the possible data arrangements based on a random assignment procedure adopted as part of an experimental design. When there has been no random assignment of treatments to participants or observation periods, no valid randomization test will be possible. Also, if there is a mismatch between the way in which treatments are randomly assigned and the way in which arrangements are generated in a randomization test, it will not be valid. We provide an example of how this might arise by revisiting the AB phase design (our Design 1).
