INFERENCE USING CONDITIONAL PROBABILITIES DESPITE PRIOR IGNORANCE

Some assumptions are introduced about ignorance and heuristic inferenc e based only upon evidence and without prior probabilities. The consis tency of the assumptions is checked by presenting a model of them. The assumptions imply a decision procedure for orderings between exclusiv e sentences which works equally well with subjectivist Bayes Factors o r the kind of functions commonly found in classical objectivist tests of statistical significance. Within this framework for representing ig norance, the sometimes contentious schools of statistical objectivism and subjectivism appear to share much in common. Two statistical appli cations are presented: significance testing of a sharp null hypothesis , and the ''perfect working'' parameter estimation problem of reliabil ity engineering. Finally, the decision procedure for exclusive sentenc es is adapted to more general cases of reasoning under uncertainty.