The Oregon Medicaid Lottery New England Journal of Medicine Baicker et. al Study Power Calculations
Austin Frakt has done the heavy lifting, and presents the power calculations that, in an ideal world, should have been done and archived ex ante as part of the experimental design of Baicker et al.: The Oregon Experiment — Effects of Medicaid on Clinical Outcomes. Needless to say, he may have made an error: this is the moral equivalent of rocket science. But with enough eyes all bugs are shallow, hopefully…
Until somebody improve and refines his calculations, I believe that the right bottom line is his:
Updated power calculation: Thestudy was underpowered for the change in proportion with elevated glycated hemoglobin (GH) by a factor of 23. Yes, twenty-three…. Let me now state where we are. With respect to the statistically insignificant physical health measures in the study… the sample was too small even for much larger effects. This renders them… uninformative about whether or how much Medicaid improves physical health. Uninformative means just that. No new information. No resetting of priors is justified… We also know, from the authors’ discussion and from Aaron’s posts, that the results include [point estimate] changes in blood sugar and blood pressure that are not unreasonable to have expected clinically [if Medicaid were effective]…. Again, no resetting of priors is warranted.
Given this, for the physical health measures only, I don’t understand the rush I’ve noticed in people updating what they expected Medicaid could do…. I think it is time for people to take another look at what this study is saying…. What I think we’re seeing is a re-expression of everyone’s priors. This study is an opportunity to do that, but it doesn’t and shouldn’t change what [priors] are. The claims that people should be changing sides from pro- to/from anti-Medicaid expansion just make no sense based on the physical health measures in this study.
On the other hand, it is perfectly acceptable--in fact, I think it is morally and scientifically required--to update your priors and shift them in a pro-Medicaid direction from the findings on emotional health and financial stress.
