Compare fairness metrics (demographic parity, equalized odds, calibration). Why can't you satisfy all of them at once?

There is no single fairness number, and a famous result proves you cannot satisfy the main three together. The signal is defining each metric precisely and explaining the impossibility, not picking one blindly. Here is the answer.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.