Comment by lblume

If one is calibrated to report proper percentages and assigns 8% to 25 distinct events, you should expect 2 of the events to occur; 4 in case of 16% and 22.5 in case of 90%. Assuming independence (as is sadly too often done) standard math of binomial distributions can be applied and used to distinguish the prediction's accuracy probabilistically despite no actual branching or experimental repetition taking place.