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IAI Actuarial Core Principles · Actuarial Statistics · Bayesian inference: priors, posteriors, loss functions and credible intervals

The posterior distribution of a claim rate parameter λ is Gamma with shape 12 and rate 4 (mean 3, variance 0.75). Under quadratic (squared error) loss, what is the Bayes estimate of λ?

The Bayes estimate under squared error loss is the posterior mean. For a Gamma distribution with shape 12 and rate 4 the mean is 12 divided by 4, which equals 3.

  1. A2.75
  2. B3.00Correct
  3. C3.25
  4. D0.75
  5. 12.00

Explanation

Under squared error loss the Bayes estimate is the posterior mean. For Gamma(shape 12, rate 4) the mean is 12/4 = 3. The value 0.75 is the posterior variance, which is not the estimate, and 2.75 is the mode (11/4), which is the answer under all-or-nothing loss.

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