This document is aimed at subcontractors doing medical research for me. I am sharing it in the hope it is more broadly useful, but have made no attempts to make it more widely accessible.

Intro

Guesstimate is a tool I have found quite useful in my work, especially in making medical estimates in environments of high uncertainty. It’s not just that it makes it easy to do calculations incorporating many sources of data; guesstimate renders your thinking much more legible to readers, who can then more productively argue with you about your conclusions.

The basis of guesstimate is breaking down a question you want an answer to (such as “what is the chance of long covid?”) into subquestions that can be tackled independently. Questions can have numerical answers in the form of a single number, a range, or a formula that references other questions. This allows you to highlight areas of relative certainty and relative uncertainty, to experiment with the importance of different assumptions, and for readers to play with your model and identify differences of opinion while incorporating the parts of your work they agree with.

Basics

If you’re not already familiar with guesstimate, please watch this video, which references this model. The video goes over two toy questions to help you familiarize yourself with the interface.

The Algorithm

The following is my basic algorithm for medical questions:

Formalize the question you want an answer to. e.g. what is the risk to me of long covid?
Break that question down into subquestions. The appropriate subquestion varies based on what data is available, and your idea of the correct subquestions is likely to change as you work.
1. When I was studying long covid last year, I broke it into the following subquestions
  1. What is the risk with baseline covid?
  2. What is the vaccine risk modifier?
  3. What is the strain risk modifier?
  4. What’s the risk modifier for a given individual?
In guesstimate, wire the questions together. For example, if you wanted to know your risk of hospitalization when newly vaccinated in May 2021, you might multiply the former hospitalization rate times a vaccine modifier. If you don’t know how to do that in guesstimate, watch the video above, it demonstrates it in a lot of detail.
Use literature to fill in answers to subquestions as best you can. Unless the data is very

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