In probability theory and related fields, a stochastic or random process is a mathematical object usually defined as a family of random variables.
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In probability theory and related fields, a stochastic or random process is a mathematical object usually defined as a family of random variables.
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Term random function is used to refer to a stochastic or random process, because a stochastic process can be interpreted as a random element in a function space.
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The values of a stochastic process are not always numbers and can be vectors or other mathematical objects.
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Stochastic or random process can be defined as a collection of random variables that is indexed by some mathematical set, meaning that each random variable of the stochastic process is uniquely associated with an element in the set.
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Stochastic process can be classified in different ways, for example, by its state space, its index set, or the dependence among the random variables.
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When interpreted as time, if the index set of a stochastic process has a finite or countable number of elements, such as a finite set of numbers, the set of integers, or the natural numbers, then the stochastic process is said to be in discrete time.
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The term stochastic process first appeared in English in a 1934 paper by Joseph Doob.
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The first written appearance of the term random process pre-dates stochastic process, which the Oxford English Dictionary gives as a synonym, and was used in an article by Francis Edgeworth published in 1888.
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In other words, a Bernoulli Stochastic process is a sequence of iid Bernoulli random variables, where each coin flip is an example of a Bernoulli trial.
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Wiener process is a stochastic process with stationary and independent increments that are normally distributed based on the size of the increments.
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Almost surely, a sample path of a Wiener Stochastic process is continuous everywhere but nowhere differentiable.
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The process has many applications and is the main stochastic process used in stochastic calculus.
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The Stochastic process is used in different fields, including the majority of natural sciences as well as some branches of social sciences, as a mathematical model for various random phenomena.
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Poisson process is a stochastic process that has different forms and definitions.
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The number of points of the Stochastic process that are located in the interval from zero to some given time is a Poisson random variable that depends on that time and some parameter.
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For example, a stochastic process can be interpreted or defined as a -valued random variable, where is the space of all the possible functions from the set into the space.
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An increment of a stochastic process is the difference between two random variables of the same stochastic process.
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Where is a probability measure, the symbol denotes function composition and is the pre-image of the measurable function or, equivalently, the -valued random variable, where is the space of all the possible -valued functions of, so the law of a stochastic process is a probability measure.
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Stationarity is a mathematical property that a stochastic process has when all the random variables of that stochastic process are identically distributed.
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The index set of a stationary stochastic process is usually interpreted as time, so it can be the integers or the real line.
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One example is when a discrete-time or continuous-time stochastic process is said to be stationary in the wide sense, then the process has a finite second moment for all and the covariance of the two random variables and depends only on the number for all.
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Separability is a property of a stochastic process based on its index set in relation to the probability measure.
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Markov chain is a type of Markov Stochastic process that has either discrete state space or discrete index set, but the precise definition of a Markov chain varies.
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Symmetric random walk and a Wiener Stochastic process are both examples of martingales, respectively, in discrete and continuous time.
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Point Stochastic process is a collection of points randomly located on some mathematical space such as the real line, -dimensional Euclidean space, or more abstract spaces.
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The Stochastic process is a sequence of independent Bernoulli trials, which are named after Jackob Bernoulli who used them to study games of chance, including probability problems proposed and studied earlier by Christiaan Huygens.
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Bernoulli's work, including the Bernoulli Stochastic process, were published in his book Ars Conjectandi in 1713.
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Poisson Stochastic process is named after Simeon Poisson, due to its definition involving the Poisson distribution, but Poisson never studied the Stochastic process.
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Stochastic process then found the limiting case, which is effectively recasting the Poisson distribution as a limit of the binomial distribution.
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Stochastic process introduced and studied a particular set of Markov processes known as diffusion processes, where he derived a set of differential equations describing the processes.
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Furthermore, if a stochastic process is separable, then functionals of an uncountable number of points of the index set are measurable and their probabilities can be studied.
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