Double Blind – In a multi-group study, both the researchers and study participants are blinded to which group is receiving which treatment. This can apply to both placebo-controlled studies in which one group receives a placebo as well as comparative studies in which both groups receive different treatments.

Single Blind – Only the researchers or only the participants are blinded, though most commonly it refers to participants.

Open Label – Both the researchers and participants are aware of the actual treatment they are receiving – there is no blinding.

Crossover – In a crossover study both groups receive both treatments. After group A finishes the first leg of the study there is typically a washout period then group A moves onto the second leg of the study. Group B does the opposite. This allows each person to serve as his or her own control, meaning post-treatment results can be compared against baseline values for each person. This method helps account for variances in results due to individual biology and lifestyle factors.

Pilot  – The first study of its kind; if pilot studies show promising results follow-up studies are typically done to determine if the results can be replicated.

In Vitro – A study performed on a cellular level, not within a living organism. Test tube studies are examples of in vitro studies

In Vivo – A study performed on a living organism. Human and animal studies are examples of in vivo studies.

Attrition – Study participants that are drop out during the study period, commonly due to side effects