Category Archives: Statistics

PMean: Extremely imbalanced multi-center trials

There was some recent discussion of issues with multi-center trials where one center dominates, contributing as much as 94% of all the patients. What does this do to the generalizability of the study. I wanted to summarize these comments here, because it relates to some of the issues I’m looking at right now in accrual models for multi-center trials. Continue reading

PMean: How big is the stuff I’m working on

I have been working part-time on a project for the Great Plains Collaborative (GPC) under the direction of Russ Waitman and the gentle guidance of Dan Connolly, both at Kansas University Medical Center. I hoping to submit a paper soon on the work I’ve done, but if you are curious about the size and scope of the electronic health records that I’ve been slinging around, this blog entry might help. Continue reading

Recommended: Medicare Claims Synthetic Public Use Files (SynPUFs)

The Centers for Medicare & Medicaid Services (CMS) provides researchers with access to Medicare claims data, which is a wonderful resources. But you have to sign a restrictive agreement before they will give you this data and you have to pay a non-trivial amount of money to get the data. Fair enough, because CMS has to guarantee patient confidentiality among other things. But what if you want to “play” with the data before taking the plunge? Thankfully, CMS has provided to the general public a synthetic (read fake) data set that has the same data structure. This allows you to prototype your programs on the synthetic data and then transition easily to the real data. Continue reading

PMean: Cases and cohorts and controls, oh my!

Some asked a question about a retrospective study where you have a control cohort matched to a case cohort so the cohorts are similar on important (potentially confounding) variables. I pointed out that the two consecutive words “case cohort” are ambiguous and tried to explain¬† how I define a retrospective cohort design versus a (retrospective) case-control design. Continue reading