Types of Clinical Research Studies

Treatment studies

•Randomized controlled trial
–Double-blind randomized trial
–Single-blind randomized trial
–Non-blind trial

•Nonrandomized trial (quasi-experiment)
–Interrupted time series design (measures on a sample or a series of samples from the same population are obtained several times before and after a manipulated event or a naturally occurring event) - considered a type of quasi-experiment

Observational studies
•Cohort study
–Prospective cohort
–Retrospective cohort
–Time series study

•Case-control study
–Nested case-control study

•Cross-sectional study
–Community survey

Presently for orthopedic literature the following heirarchy of evidence is followed in most peer reviwed journals