“*Probabilities obtained by maximum entropy cannot be relevant to physical predictions because they have nothing to do with frequencies*.” E.T. Jaynes, PT, p.366

“*A frequency is a factual property of the real world that we measure or estimate. The phrase `estimating a probability’ is just as much an incongruity as `assigning a frequency’. The fundamental, inescapable distinction between probability and frequency lies in this relativity principle: probabilities change when we change our state of knowledge, frequencies do not*.” E.T. Jaynes, PT, p.292

**A** few days ago, I got the following email exchange with Jelle Wybe de Jong from The Netherlands:

**Q.** I have a question regarding your slides of your presentation of Jaynes’ *Probability Theory*. You used the *[above second]* quote: Do you agree with this statement? It seems to me that a lot of ‘Bayesians’ still refer to ‘estimating’ probabilities. Does it make sense for example for a bank to estimate a probability of default for their loan portfolio? Or does it only make sense to estimate a default frequency and summarize the uncertainty (state of knowledge) through the posterior? Continue reading →