Define your north star metric, 2-3 supporting metrics, and at least one guardrail metric before you launch anything.
Strong answers define a metric hierarchy: north star (activation rate), leading indicators (step completion rates, time-to-value), and guardrail metrics (support tickets, drop-off rates). Candidates should mention A/B testing methodology, statistical significance, and setting targets before launch.
Tests analytical rigour. Weak candidates pick vanity metrics. Strong candidates think about what "good" looks like before measuring, and account for potential negative side effects.