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In statistics, a proxy or proxy variable is a variable that is not in itself directly relevant, but that serves in place of an unobservable or immeasurable variable. [1] In order for a variable to be a good proxy, it must have a close correlation, not necessarily linear, with the variable of interest. This correlation might be either positive ...
Examples of proxies include stable isotope measurements from ice cores, growth rates in tree rings, species composition of sub-fossil pollen in lake sediment or foraminifera in ocean sediments, temperature profiles of boreholes, and stable isotopes and mineralogy of corals and carbonate speleothems. In each case, the proxy indicator has been ...
A paleothermometer is a methodology that provides an estimate of the ambient temperature at the time of formation of a natural material. Most paleothermometers are based on empirically-calibrated proxy relationships, such as the tree ring or TEX 86 methods.
The blue line represents global surface temperature reconstructed over the last 2,000 years using proxy data from tree rings, corals, and ice cores. [1] The red line shows direct surface temperature measurements since 1880. [2] Global surface temperature (GST) is the average temperature of Earth's surface.
Tree-ring width, for example, is considered a reliable proxy of ambient environmental conditions such as the warmth of growing seasons or amount of rainfall. Although scientists cannot directly measure the temperature of past years, tree-ring width and other climate proxies have been used to provide a semi-quantitative record of average ...
Routine health outcomes measurement is the process of examining whether or not interventions are associated with change (for better or worse) in the patient's health status. This change can be directly measured (e.g. by rating scales used by the clinician or patient) or assumed by the use of proxy measurement (e.g. a blood test result).
Infrared temperature measurement instruments used in planetary missions include surface temperature measurements taken by the Thermal Emission Spectrometer (TES) instrument on Mars Global Surveyor and the Diviner instrument on the Lunar Reconnaissance Orbiter; [32] and atmospheric temperature measurements taken by the composite infrared ...
The presence of indicator bacteria is measured in a variety of ecosystems and sometimes alongside other measurements. In the Great Lakes, a study was conducted testing for both fecal indicator bacteria (FIB) concentrations and pathogen gene markers. [7] The FIB measured in this study included fecal coliform bacteria, E. coli, and enterococci. [7]