I've interviewed more people that I can remember as a hiring manager for massive businesses and as a recruiting leader for over a decade at Procter & Gamble. And honestly, I wish I would have thought of this one question I just discovered from bestselling management author, Suzy Welch. Welch recently told CNBC Make It that this killer question can become the deciding factor in an interview, and if handled correctly, can help the candidate to really stand out.

The question is: "What did you do to prepare for this interview?"

Welch says it's your chance to learn more about how a candidate approaches responsibilities. She related a tale-of-two-cities story to prove the point. One job candidate looked perfect on paper and was rolling along in the interview until Welch asked the killer "What did you do to prepare" question. The surprised response was, "Um, I looked for your office on Google Maps."

Compare that to the response of the person who got hired, which revealed that she'd scouted the parking lot situation the night before, read everything that Welch wrote and had studied her employer, NBC, as well. 

Which one would you hire?

Here's why it's such a brilliant interview question. You can learn so much from this one question. You'll get a great sense for how prepared and thorough of a person the candidate is, how creative they are, and how much grit and resourcefulness they have. You'll get a sense for what kind of passion and energy they'll bring to the job on day one. You'll also learn how much they really want the job, important in a day and age of employee ghosting.

I also think that it speaks to the humility of the candidate. Anyone who merely "Google mapped" you probably thinks too highly of themselves and how they'll do in the interview. I'll take a humble, over-prepared candidate over a brash, "just roll with it" candidate any day — even if the latter exudes confidence and glossiness in the interview.

Finally, it's a question difficult to fumble your way through. By definition, what you did to prepare for the interview will be super-top of mind and should be recallable in an instant. Anyone who fumbles around and hesitantly shares their string of preparatory events is likely making it up.

So if you're an interviewer, it helps to question your questions from time to time. While you're at it, make time for this deceivingly simple, but oh-so-powerful nine-word inquiry.