The realization (the “result”, the observed value) of a random variable (say, a dice roll) is a number – (but, as it’s a random variable, we know that the number can take values from a given set according to some probability law). The use of the term “random process” pre-dates that of “stochastic process” by four or so decades. In music, mathematical processes based on probability can generate stochastic elements. In other words an act of God is random, but a hurricane hitting the east coast of the US is stochastic event. Any individual hurricane may be random but it also exists as a mathmatical probability within a system of many hurricanes that hit or do not hit the east coast every year. A coin flip has an interesting difference than a hurricane since each individual flip of a coin is already stochastically limited to the 50% statistical probability of two possible results.

Similarly “stochastic process” and “random process”, but the former is seen more often. They are used in phrases such as “random variable,” “random walk,” “stochastic process,” “stochastically complete,” etc, which have accepted definitions of their own. In all cases both words tend to refer to an element of chance or unpredictability. But they are generally not interchangeable; if you talk about a “stochastic walk” people will be confused. Funny enough, in Russian literature the term “stochastic processes” did not live for long.

What is a Stochastic Process?

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