Key Takeaways:

- Epistemic probability is incomplete information about how probabilities arise.
- The field bridges the gap between known measurements and what is thought to be true.
- An example is classical statistical mechanics.

**Epistemic probability** concerns “…our possession of knowledge, or information.” It is incomplete knowledge about the mechanism from which the probabilities are derived. A common use of the term is to define how much support is given by all the available evidence; it can be measured in “degrees of belief” or “degrees of rational belief”.

The term **Epistemic** comes from philosophy and means:

“…namely the degree of belief in the occurrence of the state of affairs, the willingness to act on its assumption, a degree of support or confirmation, or similar” [1].

## Types of Epistemic Probability

Epistemic probability merges traditional statistics, approaching the problem from the viewpoint of epistemic attitudes. These probabilities can be:

**Doxastic**: Opinions about data and hypotheses, with a strength of belief.**Decision-theoretic:**Builds on doxastic in a more elaborate way, figuring out dispositions towards actions and decisions relating to data and hypotheses.**Logical:**A formal framework for epistemic probability, comparable to truth values in deductive logic.

## Example of Epistemic Probability from Quantum Mechanics

One example of the use of epistemic probability is to assign probabilities to the possible truth of a proposed law of physics. In quantum mechanics, there are two different approaches to determining probabilities in quantum mechanics. The more fundamental way is through Brownian motion, a type of stochastic process. However, classical statistical mechanics, which is deterministic, is epistemic probability—the probabilities emerge because of incomplete descriptions [2]. The gap between what is measured and what is thought to be true is achieved through development of an epistemic probabilistic framework.

**References:**

Image: Voyajer at the English-language Wikipedia,

[1] Stanford Encyclopedia of Philosophy. Philosophy of Statistics. Retrieved October 22, 2021 from: https://plato.stanford.edu/entries/statistics/

[2] Saunders, S. What is Probability? Retrieved October 22, 2021 from: https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.252.8105&rep=rep1&type=pdf

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