An investigation aimed at ascertaining the status of a set of variables, such as the number and variety of persons with specific conditions in a specified population, but without any critical analysis or attempt to test casual hypotheses, is known as a descriptive study. Examples include the U.S. National Health Care Survey, periodic reports from cancer registries, and needs assessment surveys conducted by a local health department. Descriptive studies can yield valuable information about a population's health status, and they can be used to measure risks and generate hypotheses. Descriptive studies are also useful in health service evaluation and can be used periodically to determine whether a particular service is improving, for instance, if serial description studies all show evidence of reduced sickness or disability rates over a period of years.
JOHN M. LAST