Tell me about a time you solved a problem with incomplete information

Why interviewers ask this

Real problems rarely come with complete specifications. This checks whether you can make reasonable progress and good decisions despite genuine uncertainty, rather than stalling until everything is clarified.

What a strong answer covers

• What information was missing, specifically, and why it wasn't available (no one had the answer yet, getting it would take too long, the situation was genuinely novel)
• How you decided to proceed anyway — what assumptions you made explicit, and how you chose them
• How you reduced risk given the uncertainty — a reversible first step, a small experiment, a checkpoint to validate assumptions before going further
• What you learned once more information became available, and whether your initial assumptions held up

Common pitfalls

• A story where the "incomplete information" was really just normal ambiguity you should have been able to resolve by asking one question
• No mention of explicit assumptions — proceeding on unstated assumptions is a much weaker signal than proceeding on stated, checkable ones