If you are designing a retrospective chart review, you should talk to a statistician early in the process. There are lots of statistical issues that you must think about during the concept development phase of your research. Here is a broad overview of these issues. Continue reading →

Dear Professor Mean, I could use some advice on defining and following analysis plans for research proposals. I can see how in well-trodden research, where the nuances of the data are well understood, and reasonable distributional assumptions are already identified, a detailed analysis plan may be straightforward to develop. But what about cases where you collect observational data, and though you may have specific hypotheses in mind prior to collecting it, you can’t really pin down the most appropriate analysis until after you’ve done some exploration? Is there generally an acceptable amount of leeway in cases like these, where your analysis doesn’t follow the original plan to the dot, but it’s still designed to address the same question? Or must one be as specific and detailed in the plan as possible, and consider every contingency (e.g., if the distribution is noisy, switch to this non-parametric test)? Or does it really vary with whoever the reviewer is? Continue reading →

I got a question that I had never heard before, and it sort of is a statistics question and sort of isn’t. A researcher was comparing two methods of training residents in a particular surgical procedure and wanted to know how long you should wait between the training and the evaluation of whether that training was effective. Continue reading →