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Re: [Phys-L] six days

An exponential model makes fairly good agreement with the official data for total cases.
When a non linear regression app makes the fit
fall below R^2 = 0.95, a logistics model (of the kind used to fit the HIV epidemic well) starts to show a decline in "carrying capacity" i.e the point at which all the people who can be infected ARE infected and the exponential growth smooths out to a flat top, showing  that high point falling from many millions to a relatively smaller number in the last few days for Oklahoma.(population 3M+)
 It takes several days of below expected exponential growth for a curve fitter to invoke a smaller value for the "carrying capacity"in a logistic model - and that's what we have today - but it is likely just a pot-hole in the progression. If the shortfall in growth continues long enough, one will gain some confidence in predicting the top. Modelers who are paid to work in this area prefer the NEW cases per day, rather than the total cases. This has the usual problem of working from a change in numbers rather than the total numbers - it is very noisy, so that these folk use weekly new cases to smooth out their pot-holes. The graphs here use a more sensitive, but not very noisy, daily data method.

Brian W

On 3/29/2020 9:10 PM, Bill Norwood via Phys-l wrote:
Hi Brian Whatcott,
- Sorry, I’m dense on this one.
- I need something I can share with relatives.
- Cyp explain more verbosely.
Many thanks!
Bill Norwood

Sent from my iPhone

On Mar 29, 2020, at 6:41 PM, brian whatcott <> wrote:

On 3/29/2020 2:24 AM, bernard cleyet wrote:
and no posts. Have we all succumbed to the corona?

bc soon worried.
Forum for Physics Educators
I pinned up the local (Oklahoma) statistics for cases with time.
My logistic plot saw a downturn in the rate of infection for three days, and so it revised its peak population infected line from millions to ~ a thousand. It SO over reacts to good news!

[sorry for the previous post - out of practice sharing with Phys-l!] } } } See correction above!

Brian W
Forum for Physics Educators
Forum for Physics Educators