Soheila Rezakhani - Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Science, Kerman, Iran

Clinical research generally is consisting of two types of study that are observational and experimental. First one can be descriptive or analytic. Descriptive studies included Case report, Case series, Cross sectional survey. Analytic studies included case-control and cohort. Case series are weakest research design and cohort studies are strongest one. Cross-sectional study is the only study capable of calculating prevalence. Randomized clinical trials is an experimental study that measure treatment effect