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Saddle point
A saddle point is a critical point of a function that is neither a local maximum nor a minimum; nearby, the function takes both larger and smaller values.
Saddlepoint approximation method
The saddlepoint approximation method is a statistical technique, introduced by H. E. Daniels in 1954, for approximating densities and tail probabilities from a cumulant generating function, more accurately in the tails than the normal approximation.
Safety integrity level
A safety integrity level (SIL) is one of four levels, SIL 1 lowest to SIL 4 highest, specifying safety integrity requirements of safety functions under the IEC 61508 standards.
SageMath
SageMath, formerly Sage, is a free, open-source mathematics software system started in 2005 by William Stein as an alternative to Magma, Maple, Mathematica, and MATLAB.
Salem–Spencer set
A Salem–Spencer set is a finite set of numbers containing no three-term arithmetic progression. Salem and Spencer proved in 1942 that such sets can be surprisingly large.
Sally C. Morton
Sally C. Morton is an American biostatistician specializing in meta-analysis who leads research at Arizona State University and is a past president of the American Statistical Association.
Sample entropy
Sample entropy (SampEn) is a complexity measure for time series that estimates the probability that similar segments stay similar one point later; higher values mean more irregular signals.
Sample size determination
Sample size determination, also called sample size calculation, is the process of deciding how many participants or observations a study needs for adequate precision or statistical power.
Sample space
The sample space, also called the possibility space or sample description space, is the set of all possible outcomes of a random experiment, denoted Ω.
Sampling (statistics)
Sampling in statistics, or statistical sampling, is selecting a subset of a population so measurements on it can estimate characteristics of the whole, at far less cost than a census.
Sampling bias
Sampling bias, also called ascertainment bias, is the systematic deviation of a sample from the population it is meant to represent, often caused by flawed selection.
Sampling distribution
A sampling distribution is the probability distribution of a statistic, such as a sample mean, over all possible samples of a given size drawn from the same population.
Sampling error
Sampling error, or sampling variation, is the part of a survey estimate's difference from the true population value that arises because only a sample was measured.
Sampling with replacement
Sampling with replacement is a sampling method in which each drawn unit is returned to the population before the next draw, making the draws independent and identically distributed.
Sankey diagram
The Sankey diagram, also called a Sankey plot, is a flow diagram whose band widths are proportional to the quantities flowing, named after Captain Matthew Sankey.
Sard's theorem
Sard's theorem, also known as the Morse-Sard theorem, is a result in differential topology stating that the critical values of a smooth map between manifolds have measure zero.
SAS (software)
SAS, also known as the SAS System, is a proprietary statistical software suite developed by SAS Institute, founded in Cary, North Carolina, in 1976, and widely used in pharmaceutical and clinical research.
Satisfaction relation
The satisfaction relation in logic holds between a structure, a formula, and an assignment of objects to variables, written M, s models φ, and was introduced by Alfred Tarski in 1933.
Satisfiability
Satisfiability is the property of a logical formula being true under at least one interpretation, or model. Its decision problem spans NP-complete Boolean SAT and undecidable first-order logic.
Satisfiability modulo theories
Satisfiability modulo theories (SMT) is the decision problem of whether a formula is satisfiable under a background theory, extending Boolean SAT to first-order logic for verification.
Satisfiability threshold
The satisfiability threshold is the critical clause-to-variable density at which a random k-SAT formula changes from satisfiable to unsatisfiable with high probability as variables grow.
SaTScan
SaTScan is free software created by biostatistician Martin Kulldorff that detects and evaluates statistically significant spatial, temporal, and space-time clusters of events such as disease cases.
Saturated model
A saturated model, also called a saturated structure, is a model of a first-order theory realizing every type over smaller parameter sets, a key concept from Morley and Vaught's 1962 paper.
Saturation arithmetic
Saturation arithmetic, also called clamped or clipped arithmetic, is computer arithmetic in which overflowing results clamp to the largest or smallest representable value instead of wrapping.
Saturation number
The saturation number sat(n, H) is the minimum number of edges in an n-vertex graph that is maximal H-free, the minimizing counterpart of the Turán number.
Sauer–Shelah lemma
The Sauer–Shelah lemma, also called the Perles–Sauer–Shelah lemma, is a combinatorics theorem bounding a set family's size by its VC dimension, with applications in machine learning.
Saul Kripke
Saul Kripke, or Saul Aaron Kripke, was an American philosopher and logician, 1940 to 2022, whose Naming and Necessity and possible worlds semantics reshaped analytic philosophy.
Sawtooth wave
The sawtooth wave, or saw wave, is a periodic waveform that rises or falls linearly each cycle and then jumps back, resembling saw teeth; it contains every harmonic and is standard in sound synthesis.
ScaLAPACK
ScaLAPACK (Scalable Linear Algebra PACKage) is a library of high-performance linear algebra routines for parallel distributed-memory machines, solving linear systems, least squares, eigenvalue, and singular value problems, first released in 1995.
Scalar (mathematics)
A scalar is a quantity expressible by a single number, such as mass or temperature; in linear algebra, the elements of a field over which a vector space is built.