What is the method to deal with contamination in experimental designs?

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Contamination occurs when the interaction between individuals randomly assigned to different treatment conditions causes some individuals to receive features of a treatment to which they were not assigned. It is suggested to adopt a cluster-randomized design to minimize contamination by ensuring greater physical separation between individuals in the intervention and control groups. The cluster-randomized randomly assigns entire clusters of individuals (e.g., schools and classrooms) to treatment or control groups.