Case-control or case-comparison study, retrospective study Quantitative research in which persons with a disease (or other outcome) of interest and a suitable control group of persons without the disease are studied. The relationship of an attribute to the disease is examined by comparing the diseased and nondiseased with regard to how frequently the attribute is present. Risk is estimated by the odds ratio.
Causality The relationship of causes to the effects they produce. A cause is termed “necessary” when it must always precede an effect; this effect need not be the sole result of the one cause. A cause is termed “sufficient” when it inevitably initiates or produces an effect. Any given causal factor may be necessary, sufficient, neither, or both.
Cluster randomization design An experiment in which clusters of individuals rather than independent individuals are randomly allocated to the intervention group.
Cohort study A method of study in which subsets of a defined population can be identified who are, have been, or in the future may be exposed or not exposed, or exposed in different degrees, to a factor or factors hypothesized to influence the probability of occurrence of a given disease or other outcome. The main feature of cohort studies is observation of large numbers of individuals over a long period (commonly years), with comparison of incidence rates in groups that differ in exposure levels. Risk is estimated by the relative risk.
Community A social entity that can be either spatial (based on where people live in local neighborhoods, residential districts, or municipalities) or relational (based on common ethnic, cultural, or other characteristics or similar interests).
Community assessment (needs assessment) A procedure used to collect data that describe the needs and strengths of a specific group, community, or population.
Comparative effectiveness research Research involving the generation and synthesis of evidence that compares the benefits and harms of alternative methods for preventing, diagnosing, treating, and monitoring health conditions in a real-world setting.
Comparative experiment A study that compares the effects of a program or policy against a comparison condition or control group.
Content analysis A systematic and objective summary of the concepts of text.
Context The set of factors or circumstances that surrounds a situation or event and gives meaning to its interpretation; the broader environment in which a program operates.