What is Bayesian Evidence?

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Could someone explain this concept or give a link to the explanation of this concept please? I know what "Bayesian" is, but I don't know what "Bayesian evidence" is. A good explanation of "evidence" will also be appreciated.

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This is a concept used in Bayesian model selection. Essentially, it's the probability of the data in some model $\mathcal{M}$ when the parameter uncertainty has been integrated out. Mathematically, it is

$$ Pr(D|\mathcal{M})=\int_{\Theta}Pr(D|\theta)Pr(\theta|\mathcal{M})d\theta $$ where $\Theta$ is the domain of $\theta$. Using the evidence of different models you can compute the Bayes factor, for example.

See this for further reading.