Final answer:
A level 2b study on the USC Evidence Pyramid is a cohort study. It is an observational study where a group of similar subjects is selected and followed over time. Cohort studies provide reliable data on the progression of disease states or other conditions of interest.
Step-by-step explanation:
The level 2b study on the USC Evidence Pyramid is a cohort study. A cohort study is an observational study in which a group of similar subjects is selected at the beginning of the study and followed over time. Researchers collect data on the cohort periodically and can establish the sequence of progression of disease states or other conditions of interest. This type of study is prospective and provides more accurate data compared to self-reported recall data in case-control studies.