8 November - December - 2020 You May be Using the Wrong Model and it Will Cost YouBy Jordan S. Peck, Vice President, Physician Practice Operations, Southern Maine Health CareAs the world continues to face the challenges related to forecasting COVID-19 and its effects on all parts of our economy, the general population is becoming familiar with a concept that was summarized by a statistician, George Box; "All models are wrong." Modelers often frame their presentations with this phrase, usually appending, "some are useful." Forecasting models are a fundamental element of our daily life. While there are many complex, industry specific examples, we all use weather forecasting models. You may have experienced the situation where a weather forecast says that it should be raining right now. Yet, when you look out your window, it is sunny. How do you react to that "wrong" model? If you need to get the mail, it is unlikely that you will put on a raincoat. If you are headed to a day at the park, despite the current sun, you might bring an umbrella.As COVID-19 rapidly spreads across the world, forecasting models are being spread nearly as quickly. The American Hospital Association has even published a website for tracking and explaining each of these different models. Unlike weather models, which are often designed for a normal consumer, these models are not intuitive and are prone to misinterpretation.Anyone who seeks to use one of these models must remember that models are built with a purpose and the conclusions drawn from that model should be limited to that purpose. Even when limiting conclusions in this way, we often recognize that the results of the model are true for are presentative system that is similar to the real life system, but it is not exact. In this way the model is, by definition, "wrong." The results of these models are used to provide a consumer with a sense of the non-linear dynamics of the live system and a magnitude for potential outcomes (i.e. does my hospital need 5 or 500 beds; as opposed to 5 or 6 beds). The prominent models being used during the current crisis are called Susceptible, Exposed, Infectious, and Recovered or "SEIR" models. The exponential nature of disease spread causes these models to be extremely volatile. Five Thirty Eight developed a lengthy "comic strip" which describes the difficulties of developing one of these models. One might read about the complexity of developing an SEIR model and how easily the model can go "wrong" and wonder why we even do it. They are developed for a particular purpose: to provide a sense of population dynamics and advise policy making. The model may incorrectly estimate the number of COVID-19 cases by an order of thousands, but it will correctly assess the relative impact of different social distancing measures and inform the IN MY OPINION
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