More than a week after some very smart health economists released findings from a study of Medicaid in Oregon, policy experts, politicians, and pundits are still arguing over exactly what the study showed—and how, if at all, it should change what we think about making health insurance more available to the poor.

That’s good. The study should force all of us, on the left and the right, to think more carefully about how we write and talk about health care reform. And I’ve read plenty of writers doing just that. But the idea that this study all but blows away the case for the Medicaid expansion, as some Obamacare critics have suggested, still strikes me as wrong-headed. And that’s because these critics make two unfair claims: that the study “proves” Medicaid doesn’t improve health and that financial security, which Medicaid clearly provided its Oregon beneficiaries, was an afterthought in the health care reform debate.

A refresher, for those of you who decided not to read the wonky set over the last ten days or so: A few years ago, when Oregon officials had to allocate 10,000 Medicaid slots from among about 90,000 applicants, they decided to use a lottery. That created two groups, randomly selected: One with an opportunity to enroll in Medicaid, one without the opportunity. Past studies of Medicaid suffered because those studies didn’t have such random assortment between people who were on the program and those who were not. People who enrolled on Medicaid tended to be poorer and sicker; researchers would adjust for that fact, but the adjustments might not have been correct. The Oregon Medicaid lottery made it possible for researchers to make a cleaner comparison of the two groups.

The headline from the study (at least on the right) is that the Medicaid beneficiaries didn't see statistically significant improvements in physical health. That's true. But it's important to understand what exactly that means. The folks on Medicaid appeared more likely to have lower blood pressure, cholesterol, and (among diabetics) blood sugar levels. But the improvement was smaller than the researchers had expected to see. And the researchers couldn't even be sure that improvement was real, because the sample size wouldn't allow them to pinpoint differences in health of that magnitude. Instead, they could give only a range of possibilities. At best, the Medicaid recipients had "clinically significant" improvements in physical health. At worst, they had no improvement at all, or perhaps even ended up in worse health.

What should we make of that? It's hard to know precisely without knowing what the researchers really should have expected in the first place. Katherine Baicker, a Harvard economist and a lead author of the paper, has said the Oregon experiment didn't produce the kind of physical health improvements researchers had found in previous studies, including the famous RAND health insurance experiment and some studies of MediCal (California's Medicaid program) during the 1980s. Aaron Carroll, a pediatrician and health care services researcher at Indiana University, thinks the comparison is flawed—that, in effect, the researchers were looking for a level of improvement that prior studies haven't really showed. I spent much of the weekend trying to sort out the particulars of this argument, via some lengthy e-mail exchanges with several of the researchers as well as some outside researchers. And I'm still not sure who’s right. Maybe they'll settle it soon.