An epidemiological study could be designed in several ways so as to collect new data. Two basic principles should always be followed: the study should be comparative and all potential causes of bias should be avoided. We can only be able to make judgments about association though comparisons. Also, Bias error can lead to erroneous conclusions about association and causation.
Four main classes of study type may be identified: descriptive studies, analytical studies, experimental studies and theoretical studies:
A descriptive study, also called a descriptive epidemiology, is to identify patterns or trends in a situation, but not the causal linkages among its different elements. Descriptive studies (such as a cross-sectional study) help in generating hypothesis on which further research may be based.
Analytical epidemiologic studies are most useful for testing an hypothesized association between human exposure and adverse health effects. Analytical study designs include case-control studies and cohort studies
An experiment or intervention study is a study in which a treatment, procedure, or program is intentionally introduced and a result or outcome is observed.
True experiments have four elements: manipulation, control, random assignment and random selection. The most important of these elements are manipulation and control
- Randomized control trial
- Clinical trial
- Community trial
A theoretical study is also called mathematical model. It is a method of simulating real-life situations with mathematical equations to forecast their future behavior. Mathematical modeling uses tools such as decision-theory, queuing theory, and linear programming, and requires large amounts of number crunching.