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Outcome test (discrimination)
The outcome test is a statistical method for detecting discrimination that compares post-decision success rates across groups rather than decision rates, introduced by Gary Becker in 1957.
Outcrop
An outcrop is a visible exposure of bedrock at the Earth's surface, where rock otherwise buried beneath soil or vegetation can be observed and sampled directly.
Outer Arm (Milky Way)
The Outer Arm is the outermost spiral arm of the Milky Way, lying beyond the Perseus Arm and carrying fewer stars than the Galaxy's dominant arms.
Outer product
The outer product of two vectors multiplies every entry of one by every entry of the other, producing an m by n matrix of rank one, written u v^T.
Outer space
Outer space is the near-vacuum region beyond the atmospheres of celestial bodies, extending from the conventional boundary above Earth through interplanetary, interstellar, and intergalactic space.
Outerplanar graph
An outerplanar graph is a graph drawable in the plane without edge crossings and with all vertices on the outer face; every outerplanar graph is planar, but K4 is not.
Outgassing
Outgassing is the release of gas from a solid material in vacuum or at elevated temperature, a key gas load in vacuum systems and contamination source in spacecraft.
Outlier
An outlier is an observation that lies an abnormal distance from other values in a sample, which may signal an error, fraud, or a real extreme value.
Outline of academic disciplines
The outline of academic disciplines, also called branches of knowledge, lists the fields of teaching and research, from broad branches like the natural sciences down to named subfields like criminology.
Outline of chemistry
The outline of chemistry, also known as the list of basic chemistry topics, is an overview of the discipline: its five classical branches, core principles like stoichiometry, neighboring fields, and recent developments.
Outline of physics
The Outline of physics is an overview article mapping the branches, fundamental theories, constants, instruments, and open problems of the natural science of matter, energy, motion, and force.
Outline of space science
The outline of space science, or space sciences, is a structured overview of the study of Earth, the solar system, and the universe using satellites and observatories.
Output coupler
An output coupler is the partially transmissive mirror at the end of a laser resonator that lets out a controlled fraction of the circulating light as the laser beam.
Outwash plain
An outwash plain is a broad, gently sloping plain of glacial sediment deposited by meltwater streams beyond a glacier's margin, known in Icelandic as a sandur.
Ouyang Ziyuan
Ouyang Ziyuan (欧阳自远, born 1935) is a Chinese geochemist and cosmochemist, the first chief scientist of China's Chang'e lunar exploration program, known as the "Father of Chang'e".
Ouzo effect
The ouzo effect, also called the louche effect, is the formation of a milky oil-in-water emulsion when water is added to anise-flavored spirits such as ouzo and pastis.
Oval
An oval is a closed plane curve resembling the outline of an egg or an ellipse; unlike the ellipse, it has no single precise mathematical definition in ordinary usage.
Ove Christiansen
Ove Christiansen is a quantum chemist and full professor at Aarhus University, known for vibrational coupled cluster theory, the CC3 model, and the MidasCpp program package.
Ove Hoegh‐Guldberg
Ove Hoegh-Guldberg, born 1959 in Sydney, is an Australian marine scientist and Emeritus Professor at the University of Queensland whose 1999 work predicted climate-driven coral reef loss by 2050.
Oven-controlled crystal oscillator
An oven-controlled crystal oscillator (OCXO) is a quartz oscillator whose crystal sits in a heated, temperature-regulated enclosure, making it the highest-stability quartz frequency reference for telecom and navigation.
Overall survival
Overall survival (OS) is the time from diagnosis, treatment start, or randomization until death from any cause, widely called the gold standard endpoint in cancer trials.
Overcontact binary
An overcontact binary is a binary star system in which both stars overfill their Roche lobes, sharing a common envelope and forming a single peanut-shaped object.
Overdetermined system
An overdetermined system is a system of equations, typically linear, with more equations than unknowns, arising in curve fitting and satellite positioning and usually solved by least squares.
Overexploitation of groundwater
Overexploitation of groundwater, also called groundwater overdraft or aquifer overexploitation, is the extraction of water from aquifers faster than they are replenished by recharge, causing declining groundwater storage worldwide.
Overhead projector
An overhead projector is a display device that throws an enlarged image of a transparency onto a screen, standard in classrooms from the 1960s to the 2000s.
Overhead stirrer
An overhead stirrer is a laboratory mixing device in which a motor above the vessel drives a shaft and impeller directly, used for volumes and viscosities beyond what a magnetic stirrer can handle.
Overlap fermions
Overlap fermions are lattice fermions introduced by Herbert Neuberger in 1997, whose Dirac operator satisfies the Ginsparg–Wilson relation exactly, giving lattice QCD exact chiral symmetry without fermion doubling.
Overlapping circles grid
An overlapping circles grid is a geometric pattern of congruent circles centered on a lattice, with radii large enough that neighbors overlap, often built on a triangular lattice.
Overlapping domain decomposition
Overlapping domain decomposition solves a partial differential equation by splitting its domain into overlapping subdomains, solving local problems in parallel, and exchanging interface data until they combine.
Overpass myth
The overpass myth, also known as the tornado overpass myth, is the mistaken belief that highway overpasses provide safe shelter from tornadoes, a practice weather agencies warn against.