Suitability of Power-Prior Exponent Specifications

Determine whether the proposed specifications of the power-prior exponent are suitable for defining the degree to which information is borrowed from source data.

Background

Power priors discount external information through an exponent applied to the source likelihood. The paper describes an approach in which the exponent is selected according to how well the observed target data are supported by a source-derived prior predictive distribution, including specifications based on a Bayesian p-value or a mapping function of the sample-size ratio.

The paper identifies an unresolved methodological issue concerning whether these exponent specifications provide an appropriate and scientifically meaningful definition of the amount of information borrowed from the source data. Although the paper develops Standardized Dynamic Borrowing as an alternative framework, it does not establish the general suitability of the cited power-prior exponent specifications.