In the ever-changing world of health care policy, measurable improvements are more important than ever-and predictable, intuitive results are the goal. But when it comes to accountable health care, data analysis can yield unexpected answers, sometimes even proving counterintuitive to practices that seemed to make sense at the time.

For that reason, developing proper analytic skills can seem like a comedy of errors, requiring patience and willingness to learn from your mistakes. Erroneous guidelines, puzzling policies, and baffling data have all been put forth in the name of improving...