how do you make a decision with incomplete information

They're testing JUDGMENT under uncertainty — a core GPS skill (field problems rarely have perfect data). Your answer structure: 1) You FIRST identify what you actually know vs what's missing. 2) You get the critical missing piece if cheap/fast (one measurement, one call). 3) If you can't wait, you make the best decision with the best available data, state your assumptions, and set a checkpoint to verify/adjust. 4) You communicate the uncertainty to stakeholders rather than hiding it. Give a real example (a diagnosis where you moved on partial data, verified later). The key phrase they want: 'I act on the best available data, name my assumptions, and verify before the decision becomes costly.' That's exactly GPS field judgment.