Types and formulations of studies used in epidemiological and clinical research.

"Study characteristics" refer to the specific design, methodology, and implementation details of a research study, which include features such as the study type, population, intervention, comparator, outcome measures, and duration, that define the clinical question being addressed and influence the validity and generalizability of the study results.

Works about clinical trials that involve at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table.

A plan for collecting and utilizing data so that desired information can be obtained with sufficient precision or so that an hypothesis can be tested properly.

Studies designed to examine associations, commonly, hypothesized causal relations. They are usually concerned with identifying or measuring the effects of risk factors or exposures. The common types of analytic study are CASE-CONTROL STUDIES; COHORT STUDIES; and CROSS-SECTIONAL STUDIES.