Every time you turn around, it seems there’s another CEO apologizing. But, when do apologies work? When does an apology help everyone learn, improve, and move on? What distinguished sincere apologies from the rest? I think it takes three ingredients:

• Compassion: The words and the tone convey sincere empathy.
• Coherence: The parts of the apology add up to a meaningful, informative statement and are not internally contradictory or self-cancelling.
• Credibility: The apology is believable and action-oriented.

Few apologies hit all three.

Let’s look at some recent examples

Recently, in her testimony before the U.S. House Energy and Commerce Committee’s Subcommittee on Oversight, General Motors CEO Mary Barra apologized after the company recalled 2.53 million cars for faulty switches. Barra offered her “sincere apologies to everyone who has been affected by this recall, especially to the families and friends of those who lost their lives or were injured. I am deeply sorry.” Barra vowed to take responsibility, and hired compensation expert Kenneth Feinberg.

In this apology, Barra showed compassion, credibility, and coherence. She not only promised but also began the process of examining what went wrong and making amends.

But Barra has received some criticism for other, related remarks in which she blamed the company’s failure to admit and act in a timely way on what she calls “the old GM.”

“It’s no ‘new GM’ if they’re doing this,” said Dartmouth Tuck School of Business professor Paul Argenti. “If this has been hidden for 10 years, there’s nothing new about the company. It’s old-school GM.”

The Guardian’s Heidi Moore agreed, urging the public not to believe Barra’s apology to Congress since the company demonstrated complete incompetence for over a decade misleading the public about mechanical failures in its cars. Worse, after accepting bailout money in 2009, GM worked hard to create the false image of a rehabilitated Detroit automaker instead of doing the necessary work to make their cars safe.

Blaming others, in other words, not only damages the credibility of the apology, it fails the coherence test.

Yahoo CEO Marissa Mayer apologized in a tweet for an email outage affecting one-million Yahoo users. Compassionate? No. Credible? Not really. Coherent? Possibly.

In February, AOL CEO Tim Armstrong received company-wide criticism for a conference call in which he linked employees’ sick babies to the company’s healt hcare insurance costs. In the same call, he blamed Obamacare for changes to the company’s 401k policy. As the criticism grew to a roar and bled beyond company lines, Armstrong sent a company-wide email acknowledging his errors, writing, “The leadership team and I listened to your feedback over the last week. We heard you on this topic,” and apologizing for his remarks. “I made a mistake and I apologize for my comments last week at the town hall when I mentioned specific health care examples in trying to explain our decision making process around our employee benefit program,” he wrote. He announced the restoration of the company’s 401k benefits matching policy.

Armstrong’s apology gains points for relevant restorative action, but is striking in its low coherence. His failure to take responsibility — blaming Obama and the distressed babies for company policies — is what inflamed the anger in the company and beyond. His response by email revealed not only a lack of compassion but also a lack of coherence: The belief that he had actually made a mistake.

In yet another example of how not to apologize, Yahoo CEO Marissa Mayer apologized in a tweet for an email outage affecting one-million Yahoo users. “We are very sorry for recent difficulties with Yahoo Mail,” she posted. The apology was insubstantial and the method of delivery was glib. Compassionate? No. Credible? Not really. Coherent? Possibly. The message isn’t extensive enough to contradict itself.

And yet another (I did say it was an epidemic): lululemon founder and CEO Chip Wilson apologized to his employees in an online video on the company’s YouTube page, a week after he offended customers by claiming the brand’s yoga pants just don’t work for “some women’s bodies.” Wilson’s apology loses points on credibility for its pseudo-personal (YouTube) method of delivery. It’s also weak on coherence because it provides no rationale for his change of heart. Finally, somehow, the compassion doesn’t ring true. He seems sadder about the effects the firestorm had on him than the effects it had on his customers.

Admit, explain, apologize, and take responsibility

In contrast, last January, Neiman Marcus CEO Karen Katz published a letter apologizing to customers for data breaches over the holiday season that exposed customer credit card data to potential theft or abuse. She offered a free year of credit monitoring service to any customer who shopped at Neiman Marcus with a payment card over the past year.

“We want you always to feel confident shopping at Neiman Marcus,” she wrote, “and your trust in us is our absolute priority.”

Her apology is coherent because it directly addresses the concerns people are likely to have about their own data – and offers immediate, relevant amends (free credit monitoring).

And it’s impossible not to mention Healthcare.gov, which unleashed a torrent of apologies, most notably from Health and Human Services Secretary Kathleen Sebelius, who apologized for the “miserably frustrating experience” people were having with the Obamacare enrollment website. Sibelius took full responsibility, showing empathy and determination: “I apologize. I’m accountable to you,” she said during testimony before a House Energy and Commerce Committee hearing. “I am committed to earning your confidence back.”

Company CEOs might learn something from the world of medicine, where doctors’ errors can have traumatic results for patients. In a prior blog in this forum, Paul Levy argues that physicians must be taught how to apologize. I couldn’t agree more. Error expert Lucian Leape, who has published widely on medical errors, disclosure, and apology, provides four stages of an effective apology: admit, explain, apologize, and take responsibility. If these stages are followed faithfully, the result is very likely to be coherent, credible and compassionate.

In a recent video interview, Leape described the critical importance of apologies for preserving trust in the doctor-patient relationship and for healing. There’s a lot of confusion over the use of the word sorry, he explains. It’s “not always an admission of liability.” If a mistake has been made, however, an apology is essential and taking responsibility is crucial for both the patient and the caregiver (who feels badly and is rarely supported by peers). “Showing remorse,” Leape explains, is a way of making amends and showing the patient that “we’re all in this together.”

In today’s complex and uncertain organizations, the compassionate, coherent, credible apology has become one of the most indispensable arrows in the leader’s quiver.

Amy Edmondson is the Novartis professor of leadership and management, Harvard Business School. This article originally appeared in athenahealth’s Health Care Leadership Forum.