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Metropolis-Hastings algorithm

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Monte Carlo approach<br />

• Basic goal lin Bayesian inference: describe posterior distribution<br />

ib i<br />

over the parameters.<br />

• Monte Carlo approach:<br />

– Sample large number of representative points from posterior.<br />

– From points, calculate descriptive statistics.<br />

• E.g., consider beta(θ | a, b) distribution:<br />

ib ti<br />

– Mean and standard deviation can be analytically derived.<br />

• Expressed exactly in terms of parameters a and b.<br />

– Cumulative probability distribution (cdf, qbeta in R) can be<br />

computed.<br />

• Used to determine credible intervals.<br />

• But: suppose didn’t know analytical formulas or cdf.

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