Prosper’s recent paper postulates that, in the absence of any prior information, the distribution of prior probabilities for an experiment should have the same symmetries as the conditional probabilities for the experiment. From this assumption, he derives a unique form for the prior probability distribution in the case of an experiment to measure a small signal above a background. His derivation does not adequately take into account the arbitrary nature of the normalization of the prior probability distribution. Allowing for changes in the normalization, the form of the prior probability distribution is no longer uniquely determined.

• Received 2 May 1988

DOI:https://doi.org/10.1103/PhysRevD.38.3582