This article was written by Wharton professor emeritus of management Michael Useem. Useem is also director of the Wharton Center for Leadership and Change Management. You are about to interview three finalists for a senior position in your enterprise. The candidates have all worked for the company for years, and your search committee believes all are qualified. What questions should you ask in the final interview to help you decide who is best qualified to lead one of your premier divisions or functions? Let’s first consider just how indicative those questions can really be. Plenty, the research suggests. Because of inadequate vettings, including final-stage interviewing, any number of companies have promoted the wrong executive to the top rung, as seen in failed successions at General Electric, Hewlett Packard, and Wells Fargo, and they have paid dearly. Elevating a suboptimal candidate into the corner office can cost you as much as 30% of your financial results over the next three years. And that difference becomes especially pronounced in an era of uncertainty and change, like now. You will certainly want to query your candidates about their vision for the company, their strategy for getting there, and their understanding of the business, but you’ll also want to get at their leadership capabilities. For that, here’s a final interview question that has worked especially well for Alex Gorsky, the former CEO and now executive chairman of one of the world’s largest publicly traded companies, Johnson & Johnson:

• What are the names of at least three executives at our company whose leadership you have significantly strengthened through your coaching and mentoring?

From my own profiling of ten CEOs regarding their company leadership, here is a vital question to foresee their potential successor’s future:

• How will you lead this enterprise when what counts ahead will be very different from what counted in the past?

If you don’t hear a lot about agility, diversity, risk, and sustainability, you probably have the wrong candidate, however otherwise qualified. And don’t limit your queries to the candidates themselves. How about asking managers who have worked for or with all the finalists whom they would choose? This question worked well at another multinational pharmaceutical, GlaxoSmithKline. A representative of the CEO and governing board asked 14 senior managers who had personal experience with the three finalists:

• Which of the three candidates to become chief executive would you most like to see elevated and to serve under?

It came as a surprise — though a very instructive one — when the subordinates converged on the dark horse, the youngest and least experienced of the three, making him the winning horse. It is also useful for you to ask other senior managers and even company directors to weigh in. When ITT split into three spin-offs, the board chair advocated promoting the parent’s CFO, Denise Ramos, to serve as one of the new CEOs. From observing her in action, he explained, she “was CEO before she was the CEO.” And if that was not already evident, it’s good to ask about it:

• If you were chief executive today, what would you do that is not already being done by the CEO?

And just in case you run out of discerning questions about your successor’s leadership:

• How will you be a better leader of this enterprise than me?

In one of the most entertaining interviews I have ever witnessed, during a parody of the Wharton’s School’s MBA admissions criteria, our director of admissions asked a candidate to sing why he should be admitted. Yes, sing. Unknown to the audience, both the admissions director and the MBA candidate had come from the opera stage. With music from a classic, their duet brought the house down. For a memorably colorful moment, you might once even stretch a little:

• Can you sing your leadership capabilities?

For ensuring the right finalist is picked, the leadership questions are not all that technical. They just need to be asked.