Knowra Random assignment (experimental design) Random assignment (experimental design) Random assignment allocates participants or experimental units to treatment groups by chance. It helps prevent systematic group differences and supports causal conclusions.
Simple randomization : An allocation method in which each unit is assigned independently by chance, usually with a fixed probability. It is the basic form of random assignment, though small samples may produce imbalanced groups.
Experimental unit : The smallest unit independently assigned to a treatment in an experiment. The unit randomized may be a person, household, classroom, or other group.
Randomized controlled trial : An experiment that randomly assigns participants to an intervention and a comparison condition. It is the best-known study design built around random assignment.
Quasi-experiment : A study that estimates intervention effects without random assignment, using an external source of comparison. It seeks causal evidence when assigning treatments by chance is unavailable or unethical.
Internal validity : The degree to which a study supports a causal conclusion for the units it examined. Random assignment strengthens causal interpretation by reducing systematic baseline differences.
Block randomization : A method that randomizes units within small groups to keep treatment counts similar throughout enrollment. It limits temporary and final group-size imbalances when participants enter over time.
Treatment group : A set of experimental units receiving the same intervention or assigned condition. Random assignment creates comparable groups whose outcomes can be contrasted.
Clinical trial : A study in people that evaluates the effects, safety, or efficacy of health interventions. Random assignment helps clinical trials estimate treatment effects without baseline selection differences.
Observational study : A study in which researchers observe exposures and outcomes without assigning interventions. Unlike random assignment, observed treatment choices can reflect participant characteristics.
External validity : The extent to which study findings apply beyond the population, setting, or conditions examined. Random assignment alone does not make a sample representative of other populations.
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