Example: We want to perform an experiment that is designed to determine which pain reliever aspirin, acetaminophen, or ibuprofen and at which dosage low or high is more effective at relieving pain after tooth extraction.

Experimental units : subjects that have had a tooth extracted

Factors: type of pain reliever, dosage

Levels: type of pain reliever: aspirin, acetaminophen, ibuprofen

dosage: low or high

Treatments: