Google values people who act on % information rather than waiting for %.
Interviewers ask: "Tell me about a time you moved forward with limited data."
Your answer should show a calculated risk, not recklessness. Explain what you knew, what you didn't know, what you did to mitigate the unknowns, and what happened.
The result doesn't have to be perfect. Google cares that you took a reasoned action rather than stalling.