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*From*: brian whatcott <betwys1@sbcglobal.net>*Date*: Mon, 13 Apr 2020 18:59:30 -0500

On 4/13/2020 10:54 AM, David Bowman wrote in part:

/snip/

It appears that a simple logistic model gives an asymptotic y_∞ value of around 32000 - 33000 US deaths (with much larger error bands) and the date of the inflection point was sometime around April 8 - 9.I found David's review helpful, particularly concerning the different exponents that may be needed, pre- and post- peak in a logistic function fit.

Nevertheless I should mention that I doubt that the simple logistic model is appropriate,/snip/ If, in the end, the model works out well it would do so only by accident. One problem with a logistic function, being the simplest function that has exponential growth at the left side end and exponential decay to an upper bound at the right side end, is that both the left side exponential growth and right side exponential decay necessarily have the *same* exponential rate. /snip/ There is absolutely no reason to expect any real contagion to possess such symmetries--even when confined to local regional values. David Bowman

I touched on this need for a more nuanced logistic non linear fit in a note I wrote today:

https://community.wolfram.com/groups/-/m/t/1936520 I used the logistic model because it [accidentally?] fit the AIDS epidemic too - rather well! Thanks Brian W

**References**:**[Phys-L] Finally ... normalized (by population) data, and Andorra***From:*bernard cleyet <bernard@cleyet.org>

**Re: [Phys-L] Finally ... normalized (by population) data, and Andorra***From:*brian whatcott <betwys1@sbcglobal.net>

**Re: [Phys-L] Finally ... normalized (by population) data, and Andorra***From:*David Bowman <David_Bowman@georgetowncollege.edu>

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