Build quality checkpoints into every phase. Catching a requirements error costs 10x less than catching it in testing and 100x less than catching it in production.
Strong answers: define quality standards upfront, build reviews into each phase (not just final delivery), use checklists and acceptance criteria, involve stakeholders in progressive validation, and address quality issues immediately rather than accumulating them. Best candidates discuss the cost of quality versus the cost of rework.
Often overlooked PM responsibility. Candidates who only check quality at delivery are accepting unnecessary risk. Look for quality integration throughout the project lifecycle.