Predictability

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Look up predictability in Wiktionary, the free dictionary.

Predictability is the degree to which a correct prediction or forecast of a system's state can be made either qualitatively or quantitatively.

Predictability and Causality

Causal determinism has a strong relationship with predictability. Perfect predictability implies strict determinism, but lack of predictability does not necessarily imply lack of determinism. Limitations on predictability could be caused by factors such as a lack of information or excessive complexity.

Laplace's Demon is a supreme intelligence who could completely predict the one possible future given the Newtonian dynamical laws of classical physics and perfect knowledge of the positions and velocities of all the particles in the world.

In experimental physics, there are always observational errors determining variables such as positions and velocities. So perfect prediction is practically impossible. Moreover, in modern quantum mechanics, Werner Heisenberg's indeterminacy principle puts limits on the accuracy with which such quantities can be known. So such perfect predictability is also theoretically impossible.

Predictability in Statistical Physics

Although the second law of thermodynamics can tell us about the equilibrium state that a system will evolve to, and steady states in dissipative systems can sometimes be predicted, there exists no general rule to predict the time evolution of systems far from equilibrium, e.g. chaotic systems, if they do not approach some kind of equilibrium. Their predictability usually deteriorates with time. To quantify predictability, the rate of divergence of system trajectories in phase space can be measured (Kolmogorov-Sinai entropy, Lyapunov exponents).

Predictability in Mathematics

In stochastic analysis a random process is a predictable process if it is possible to know the "next" state at the present time.

Predictability in Human–computer interaction

In HCI predictability is the property to forecast the consequences of a user action given the current state of the system.

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