The process of weighting involves emphasizing the contribution of some aspects of a phenomenon (or of a set of data) to a final effect or result — giving them 'more weight' in the analysis. That is, rather than each variable in the data contributing equally to the final result, some data are adjusted to contribute more than others. It is analogous to the practice of adding extra weight to one side of a pair of scales to favour a buyer or seller.
While weighting may be applied to a set of data, for example epidemiological data, it is more commonly applied to measurements of light, heat, sound, gamma radiation, in fact any stimulus that is spread over a spectrum of frequencies.
Read more about Weighting: Weighting and Loudness, Weighting in Audio Measurement, Weighting and Gamma Rays, Weighting and Television Colour Components, Weighting and UV Factor Derivation For Sun-exposure, Weighting in 3D Modeling and Animation