IAI Actuarial Core Principles · Risk Modelling and Survival Analysis · Introduction to copulas
An insurer models the annual losses from its fire and engineering portfolios. It fits a marginal distribution to each line separately and wants to combine them into a joint model without changing either marginal. By Sklar's theorem, what does the copula supply?
The copula supplies the dependence structure linking the marginals. By Sklar's theorem, a joint distribution splits into the marginal distributions and a copula, so the marginals can be fitted separately and then joined through the copula without changing them.
- AThe dependence structure linking the two marginal distributionsCorrect
- BThe marginal mean of each line of business
- CThe tail index of each individual marginal distribution
- DThe reinsurance retention for each line
- The number of claims in each line
Explanation
Sklar's theorem splits a joint distribution into its marginals and a copula. The copula carries only the dependence between the uniform transforms of the variables. Marginal features such as means and tail indices belong to the marginal distributions, not to the copula.
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