A prior is endorsed formally if it has either been derived using a formal well-established rule (in the broad sense defined by ) like the
or if it has been deduced following formal statistical arguments like
- invariance, or
- Kass, R.E. and Wasserman, L. (1996), "The Selection of Prior Distributions by Formal Rules", Journal of the American Statistical Association, Vol.91, pp. 1343-1370.