Meta-analysis. The use of statistical techniques to combine the findings of multiple independent studies. Example

Systematic review. A systematic method of identifying, selecting, appraising, and synthesizing the findings of all investigations of a specific research question. Example

Randomized controlled trial. An interventional study in which people are randomly assigned to two or more groups that receive different treatment. Example

Cohort study. A prospective observational study in which a group of people who have a certain condition or receive a particular treatment are followed over time and compared with another group of people who do not have that condition or receive that treatment. Example

Case-control study. A retrospective observational study in which two groups of people who have experienced different outcomes are compared on the basis of a supposed causal attribute. Example 

Cross-sectional study. An observational study in which the prevalence of a condition within a given population of people is assessed at one time point. Example

Case report or case series. A detailed description of a rare finding in one or more patients. Example