Demographics

Demographics are a set of characteristics used to describe or define the members of a population. Common demographic factors include age, gender, ethnicity, genetic background, and sexual orientation. Other common social factors used to describe a population include religion, income level, geographic location, education, medical conditions, behavior patterns and preferences, and so forth. Demographic information regarding the entire population of the United States or specific regions can be provided by organizations such as the U.S. Bureau of the Census, local governmental agencies, or private organizations (through survey data). The trending of demographic data can be used to allocate resources or to determine prospective markets. By looking at the size of a particular segment of the population (for example, age over 70), forecasts can be made regarding health care utilization or potential markets for medications or services that are commonly used by people in that group.

When used for research purposes, demographic data can be used to select a particular study population. This way, the prevalence of the question addressed in the hypothesis will be higher, and the required sample size will be smaller without decreasing the power of the study. Demographic data can be used to analyze a population subset from which the sample for study will be drawn. Statistics can be applied to determine if the sample selected for study matches the greater population to be examined and to determine how this is reflective of the entire population. For example, does the percentage of Asian female participants in the study match the percentage of Asian females in the population of interest, and how does this reflect the percentage of Asian females in the United States as a whole? By comparing the actual sample enrolled in the study to the population of interest, the potential unseen effects of confounding variables can be minimized and the results of the study will reflect what is expected to occur in the entire population.

In other studies, such as an epidemiologic study of a toxic exposure, the demographic data become descriptive. The age, gender, ethnicity, and so on of the exposed group can be compared with the general population as well as the incidence of a specific disease in the study group versus the general population. If the demographics of the exposed group do not match the demographics of the general population, a control group may be selected that did not have that exposure but would match the demographics of the study group. This is again done to have the two populations mimic each other, thereby minimizing the effects of other variables.