6,052 articles
National Health and Nutrition Examination Survey
The National Health and Nutrition Examination Survey (NHANES) is a CDC program of nationally representative health surveys, combining interviews, physical exams, and laboratory tests for about 5,000 Americans each year.
National Health Interview Survey
The National Health Interview Survey (NHIS) is a CDC household interview survey, conducted since 1957, that monitors the health of the U.S. civilian noninstitutionalized population.
National Institute of Statistics and Censuses (Argentina)
The National Institute of Statistics and Censuses (INDEC) is Argentina's national statistical office, created by law in 1968 to run the national census and produce official indicators like the consumer price index.
National Sample Survey
The National Sample Survey is India's continuing household survey program, run since 1950 and serving as the principal source of official data on consumption, employment, and poverty.
National Statistical Commission
The National Statistical Commission (NSC) is the apex body for India's official statistics, created by a government resolution in 2005 under the Ministry of Statistics and Programme Implementation.
National statistical offices of Africa and the Middle East
A survey of the principal national statistical offices of Africa and the Middle East, including Statistics South Africa, Kenya's KNBS, Nigeria's NBS, and Egypt's CAPMAS.
National statistical system
A national statistical system is the set of institutions in a country that produce official statistics, centered on the national statistical office and bound by statistical law.
National vital statistics reports : from the Centers for Disease Control and Prevention, National Center for Health Statistics, National Vital Statistics System
National Vital Statistics Reports (NVSR), ISSN 1551-8922, is NCHS/CDC's monthly serial since 1998 (replacing the Monthly Vital Statistics Report) publishing provisional and final U.S. birth, death, marriage, and divorce statistics from the National Vital Statistics System.
National Vital Statistics System
The National Vital Statistics System (NVSS) is the United States' official source of national birth, death, and fetal-death statistics, compiled by the National Center for Health Statistics.
Natural boundary
A natural boundary is a boundary of an analytic function's domain where every point is a singularity, blocking analytic continuation entirely, a concept introduced by Weierstrass in 1842.
Natural deduction
Natural deduction is a logical proof system, described by Gentzen and Jaśkowski in 1934, built by assuming temporary premises and discharging them, with an introduction and elimination rule for each connective.
Natural experiment
A natural experiment is a study in which an external event, not the researcher, assigns people to different levels of an intervention, permitting causal estimation from observational data.
Natural filtration
The natural filtration of a stochastic process is the filtration generated by the process itself, the smallest one to which it is adapted, recording only the process's own past behavior.
Natural logarithm
The natural logarithm, also called the natural log, is the logarithm to the base e, written ln x; it is the inverse of the exponential function.
Natural number
A natural number, or positive integer, is one of the numbers 0, 1, 2, 3, and so on, depending on convention, used for counting and ordering.
Natural transformation
A natural transformation, also called a morphism of functors, assigns to each object a morphism between two parallel functors' values, compatible with every morphism of the source category.
Navier–Stokes existence and smoothness
Navier–Stokes existence and smoothness is an open mathematics problem, one of seven Clay Millennium Prize Problems, asking whether 3D viscous fluid equations always admit unique smooth solutions.
NC (complexity)
NC, also called Nick's Class, is the complexity class of decision problems solvable in polylogarithmic parallel time with polynomially many processors, regarded as efficiently parallelizable.
Near-ring
A near-ring is an algebraic structure with addition and multiplication in which addition forms a possibly nonabelian group and multiplication distributes over addition from one side only.
Necessary condition analysis
Necessary condition analysis (NCA) is a statistical method that identifies conditions that must be present for an outcome to occur and estimates how strongly each constrains it.
Necessity and sufficiency
Necessity and sufficiency, also called necessary and sufficient conditions, are concepts in logic and mathematics: a sufficient condition guarantees a statement, and a necessary condition must hold for it.
Necklace (combinatorics)
A necklace in combinatorics is an equivalence class of fixed-length strings over a finite alphabet, where two strings count as the same if one is a cyclic rotation of the other.
Necklace splitting problem
The necklace splitting problem asks how to cut a multicolored necklace so several thieves each get an equal share of every color; Alon proved (k − 1) · t cuts always suffice.
Negabinary
Negabinary is a positional numeral system with base −2, using digits 0 and 1, in which every positive and negative integer has a unique sign-free representation.
Negative binomial distribution
The negative binomial distribution, also called the Pascal distribution, is a discrete distribution counting failures before a fixed number of successes, widely used for overdispersed count data.
Negative binomial model
The negative binomial model is a statistical model that uses the negative binomial distribution for count data whose variance exceeds its mean, underlying count regression and RNA-seq differential expression tests.
Negative binomial regression
Negative binomial regression is a regression method for count outcomes whose variance exceeds their mean, derived as a Poisson–gamma mixture and widely used in econometrics and RNA-seq analysis.
Negative number
A negative number, also called a directed number, is a real number less than zero; Brahmagupta gave early rules in 628, though Western acceptance came only in the 19th century.
Nehari manifold
The Nehari manifold is a constraint set in the calculus of variations, named after Zeev Nehari, containing every nontrivial critical point of a functional, so minimizing on it yields ground state solutions.
Neighborhood system
A neighborhood system assigns to each point of a topological space the collection of all its neighborhoods; these systems form filters and determine the topology completely.