Factorial assignment refers to a type of intervention model describing a clinical trial in which groups of participants receive one of several combinations of therapies or interventions. For example, two-by-two factorial assignment involves four groups of participants. Each group receives one of the following pairs of interventions: (1) drug A and drug B, (2) drug A and a placebo, (3) a placebo and drug B, or (4) a placebo and a placebo. So during the trial, all possible combinations of the two drugs (A and B) and the placebos are given to different groups of participants.
ClinicalTrials.gov Glossary of Common Site Terms