Descriptive research design, also known as correlational research, is a type of study in which data is collected without an alteration of the environment, according to the Office of Human Research Protections of the U.S. Department of Health and Human Services. Descriptive research involves a study in which no manipulation occurs in the process.Descriptive research typically involves a researcher observing the behavior or interaction of research subjects and recording those observations. In other descriptive studies, a researcher engages in limited interaction with subjects. This interaction, which is not manipulative in nature, usually involves a researcher interviewing the subjects included within a research group. In some cases, descriptive studies represent a preliminary step to a larger, more comprehensive course of research. A descriptive study establishes a baseline regarding certain subjects before a specific experiment that actually involves the manipulation of the subjects or their environment is initiated. Descriptive studies generally come in one of two forms. First, a cross-sectional descriptive study involves a one-time observation involving a specific group or groups of people. Second, a longitudinal descriptive study involves watching a specific group or groups of people over an established period of time. A longitudinal study can be rather short in duration or extend over the course of many years.