The process of making a study group and a comparison group in an epidemiological study comparable with respect to extraneous or confounding factors such as age, sex, weight.
- impedance m. the force delivered through the mechanical advantages of the tympanic ossicles and the area ratio of the tympanic membrane to the oval window to overcome the acoustic impedance between the ambient air and the fluid in the inner ear.
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match·ing (machґing) 1. comparison and selection of objects having similar or identical characteristics. 2. the selection of compatible donors and recipients for transfusion or transplantation. See also typing. 3. the selection of subjects for clinical trials or other studies so that the different groups being compared are similar in specified characteristics, e.g., age, sex, or race, in order to reduce bias and error caused by comparison of dissimilar groups. Matching may be on an individual (matched pairs) or a group-wide basis.Medical dictionary. 2011.