False definitely means composite.Mark Hardman wrote: ↑Tue May 05, 2020 10:30 pmDoes "probable" only include false positives or is there a possibility of false negatives as well?

True definitely means prime if n ≤ 3 317 044 064 679 887 385 961 981 and probably prime else.

The probability of a false positive is less than 1/(4^k), k is the number of tests being done. In our case we do 25 tests, so 1/(4^25) ≃ 8.9×10^(-16)