Minimum-variance Unbiased Estimator - Example

Example

Consider the data to be a single observation from an absolutely continuous distribution on with density

and we wish to find the UMVU estimator of

First we recognize that the density can be written as

Which is an exponential family with sufficient statistic . In fact this is a full rank exponential family, and therefore is complete sufficient. See exponential family for a derivation which shows

Therefore

Clearly is unbiased, thus the UMVU estimator is

This example illustrates that an unbiased function of the complete sufficient statistic will be UMVU.

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