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Signal-detection Theory
Detection theory or signal detection theory is a means to measure the ability to differentiate between information-bearing patterns (called stimulus in living organisms, signal in machines) and random patterns that distract from the information (called noise, consisting of background stimuli and random activity of the detection machine and of the nervous system of the operator). In the field of electronics, signal recovery is the separation of such patterns from a disguising background. According to the theory, there are a number of determiners of how a detecting system will detect a signal, and where its threshold levels will be. The theory can explain how changing the threshold will affect the ability to discern, often exposing how adapted the system is to the task, purpose or goal at which it is aimed. When the detecting system is a human being, characteristics such as experience, expectations, physiological state (e.g., fatigue) and other factors can affect the threshold app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stimulus (psychology)
In psychology Psychology is the scientific study of mind and behavior. Psychology includes the study of conscious and unconscious phenomena, including feelings and thoughts. It is an academic discipline of immense scope, crossing the boundaries betwe ..., a stimulus is any object or event that elicits a sensory or behavioral response in an organism. In this context, a distinction is made between the ''distal stimulus'' (the external, perceived object) and the ''proximal stimulus'' (the stimulation of sensory organs). *In perceptual psychology, a stimulus is an energy change (e.g., light or sound) which is registered by the senses (e.g., vision, hearing, taste, etc.) and constitutes the basis for perception. *In behavioral psychology (i.e., classical conditioning, classical and operant conditioning, operant conditioning), a stimulus constitutes the basis for behavior. The stimulus–response model emphasizes the relation between stimulus and behavior rather than an anim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eyewitness Identification
In eyewitness identification, in criminal law, evidence is received from a witness "who has actually seen an event and can so testify in court". The Innocence Project states that "Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in more than 75% of convictions overturned through DNA testing." This non-profit organization uses DNA evidence to reopen criminal convictions that were made before DNA testing was available as a tool in criminal investigations. Even before DNA testing revealed wrongful convictions based on eyewitness identifications, courts recognized and discussed the limits of eyewitness testimony. The late U.S. Supreme Court Justice William J. Brennan, Jr. observed in 1980 that "At least since ''United States v. Wade'', 388 U.S. 218 (1967), the Court has recognized the inherently suspect qualities of eyewitness identification evidence, and described the evidence as "notoriously unreliable", while noting tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nullspace Property
In compressed sensing, the Kernel (linear algebra), nullspace property gives necessary and sufficient conditions on the reconstruction of sparse signals using the techniques of Relaxation (approximation), \ell_1-relaxation. The term "nullspace property" originates from Cohen, Dahmen, and DeVore. The nullspace property is often difficult to check in practice, and the restricted isometry property is a more modern condition in the field of compressed sensing. The technique of Relaxation (approximation), \ell_1-relaxation The Convex optimization, non-convex \ell_0-minimization problem, \min\limits_ \, x\, _0 subject to Ax = b, is a standard problem in compressed sensing. However, \ell_0-minimization is known to be NP-hardness, NP-hard in general. As such, the technique of Relaxation (approximation), \ell_1-relaxation is sometimes employed to circumvent the difficulties of signal reconstruction using the \ell_0-norm. In Relaxation (approximation), \ell_1-relaxation, the Relaxation (a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Restricted Isometry Property
In linear algebra, the restricted isometry property (RIP) characterizes matrices which are nearly orthonormal, at least when operating on sparse vectors. The concept was introduced by Emmanuel Candès and Terence TaoE. J. Candes and T. Tao, "Decoding by Linear Programming," IEEE Trans. Inf. Th., 51(12): 4203–4215 (2005). and is used to prove many theorems in the field of compressed sensing. There are no known large matrices with bounded restricted isometry constants (computing these constants is strongly NP-hard, and is hard to approximate as well), but many random matrices have been shown to remain bounded. In particular, it has been shown that with exponentially high probability, random Gaussian, Bernoulli, and partial Fourier matrices satisfy the RIP with number of measurements nearly linear in the sparsity level. The current smallest upper bounds for any large rectangular matrices are for those of Gaussian matrices. Web forms to evaluate bounds for the Gaussian ensemble ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1708
In the Swedish calendar it was a leap year starting on Wednesday, one day ahead of the Julian and ten days behind the Gregorian calendar. Events January–June * January 1 – Charles XII of Sweden invades Russia, by crossing the frozen Vistula River with 40,000 men. * January 12 – Shahu I becomes the fifth Chhatrapati of the Maratha Empire in the Indian subcontinent. * February 26 – HMS ''Falmouth'', a 50-gun fourth-rate ship of the line built at Woolwich Dockyard for the Royal Navy, is launched. * March 11 – Queen Anne withholds Royal Assent from the Scottish Militia Bill, the last time a British monarch vetoes legislation. * March 23 – James Francis Edward Stuart, Jacobite pretender to the throne of Great Britain, unsuccessfully tries to land from a French fleet in the Firth of Forth in Scotland. * April 8 – Easter Sunday: The first performance of George Frideric Handel's oratorio ''La resurrezione'' takes place in Rome. * April ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basis Pursuit
Basis pursuit is the mathematical optimization problem of the form : \min_x \, x\, _1 \quad \text \quad y = Ax, where ''x'' is a ''N''-dimensional solution vector (signal), ''y'' is a ''M''-dimensional vector of observations (measurements), ''A'' is a ''M'' × ''N'' transform matrix (usually measurement matrix) and ''M'' < ''N''. It is usually applied in cases where there is an underdetermined system of linear equations ''y'' = ''Ax'' that must be exactly satisfied, and the sparsest solution in the ''L''1 sense is desired. When it is desirable to trade off exact equality of ''Ax'' and ''y'' in exchange for a sparser ''x'', is preferred. Basis pursuit problems can be converted to |
Compressed Sensing
Compressed sensing (also known as compressive sensing, compressive sampling, or sparse sampling) is a signal processing technique for efficiently acquiring and reconstructing a Signal (electronics), signal, by finding solutions to Underdetermined system, underdetermined linear systems. This is based on the principle that, through optimization, the sparsity of a signal can be exploited to recover it from far fewer samples than required by the Nyquist–Shannon sampling theorem. There are two conditions under which recovery is possible. The first one is sparsity, which requires the signal to be sparse in some domain. The second one is incoherence, which is applied through the isometric property, which is sufficient for sparse signals. Overview A common goal of the engineering field of signal processing is to reconstruct a signal from a series of sampling measurements. In general, this task is impossible because there is no way to reconstruct a signal during the times that the signa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Boy Who Cried Wolf
The Boy Who Cried Wolf is one of Aesop's Fables, numbered 210 in the Perry Index. From it is derived the English idiom "to cry wolf", defined as "to give a false alarm" in e''Brewer's Dictionary of Phrase and Fable'' and glossed by the ''Oxford English Dictionary'' as meaning to make false claims, with the result that subsequent true claims are disbelieved. The fable The tale concerns a shepherd boy who repeatedly fools villagers into thinking a wolf is attacking his town's flock. When an actual wolf appears and the boy calls for help, the villagers believe that it is another false alarm, and the sheep are eaten by the wolf. In a later English-language poetic version of the fable, the wolf also eats the boy. This happens in ''Fables for '' (1830) by John Hookham Frere, in William Ellery Leonard's ''Aesop & Hyssop'' (1912), and in Louis Untermeyer's 1965 poem. The moral stated at the end of the Greek version is, "this shows how liars are rewarded: even if they tell the truth, no o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Receiver Operating Characteristic
A receiver operating characteristic curve, or ROC curve, is a graphical plot that illustrates the diagnostic ability of a binary classifier system as its discrimination threshold is varied. The method was originally developed for operators of military radar receivers starting in 1941, which led to its name. The ROC curve is created by plotting the true positive rate (TPR) against the false positive rate (FPR) at various threshold settings. The true-positive rate is also known as sensitivity, recall or ''probability of detection''. The false-positive rate is also known as ''probability of false alarm'' and can be calculated as (1 − specificity). The ROC can also be thought of as a plot of the power as a function of the Type I Error of the decision rule (when the performance is calculated from just a sample of the population, it can be thought of as estimators of these quantities). The ROC curve is thus the sensitivity or recall as a function of fall-out. In general, if the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-parametric
Nonparametric statistics is the branch of statistics that is not based solely on parametrized families of probability distributions (common examples of parameters are the mean and variance). Nonparametric statistics is based on either being distribution-free or having a specified distribution but with the distribution's parameters unspecified. Nonparametric statistics includes both descriptive statistics and statistical inference. Nonparametric tests are often used when the assumptions of parametric tests are violated. Definitions The term "nonparametric statistics" has been imprecisely defined in the following two ways, among others: Applications and purpose Non-parametric methods are widely used for studying populations that take on a ranked order (such as movie reviews receiving one to four stars). The use of non-parametric methods may be necessary when data have a ranking but no clear numerical interpretation, such as when assessing preferences. In terms of levels of meas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, it would be impossible for language, relationships, or personal identity to develop. Memory loss is usually described as forgetfulness or amnesia. Memory is often understood as an informational processing system with explicit and implicit functioning that is made up of a sensory processor, short-term (or working) memory, and long-term memory. This can be related to the neuron. The sensory processor allows information from the outside world to be sensed in the form of chemical and physical stimuli and attended to various levels of focus and intent. Working memory serves as an encoding and retrieval processor. Information in the form of stimuli is encoded in accordance with explicit or implicit functions by the working memory processor. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comparative Psychology
Comparative psychology refers to the scientific study of the behavior and mental processes of non-human animals, especially as these relate to the phylogenetic history, adaptive significance, and development of behavior. Research in this area addresses many different issues, uses many different methods and explores the behavior of many different species from insects to primates. Comparative psychology is sometimes assumed to emphasize cross-species comparisons, including those between humans and animals. However, some researchers feel that direct comparisons should not be the sole focus of comparative psychology and that intense focus on a single organism to understand its behavior is just as desirable; if not more so. Donald Dewsbury reviewed the works of several psychologists and their definitions and concluded that the object of comparative psychology is to establish principles of generality focusing on both proximate and ultimate causation.Dewsbury, D. (1984). ''Comparative Psy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
