ASA Connect

 View Only
Expand all | Collapse all

A "cubic model" for COVID-19 deaths

  • 1.  A "cubic model" for COVID-19 deaths

    Posted 05-05-2020 07:42

    The Washington Post reports that the Trump Administration has rejected a Johns Hopkins based model of the Covid-19 epidemic predicting deaths rising. The article reports that in doing so, the White House is relying in part on a "cubic model" prepared by a White House economic advisor showing deaths sharply decreasing in May.

    Nate Silver attempted to reproduce the "cubic model" by putting current death figures into a spreadsheet and fitting a cubic regression. It shows deaths hitting zero on approximately May 15. (After that, being a cubic regression, the curve shows deaths becoming negative.)

    Perhaps all this is speculative. It isn't clear what the Washington Post's source meant by a "cubic model", or if Nate Silver's reproduction is accurate. We don't yet know the facts.

    But it is nonetheless a matter of concern. If this is accurate, I would respectfully suggest that the ASA, if wants to be a public interest professional association, it should be far, far more concerned about the use of junk science that gives results the audience wants to hear in major public policy decisions with life-and-death public health implications than it has been about such matters as what hour economic results get released or where a government department is located.


    If one is allowed to select from the whole gamut of possible curves, one can always find one that fits the data, appears plausible to a casual observer, and extrapolates to the future one wants to see.

    This opinion, like all of mine here, is mine only and does not represent my employer.

    https://www.google.com/amp/s/www.washingtonpost.com/health/government-report-predicts-covid-19-cases-will-reach-200000-a-day-by-june-1/2020/05/04/02fe743e-8e27-11ea-a9c0-73b93422d691_story.html%3foutputType=amp


    https://mobile.twitter.com/natesilver538/status/1257476755574718470



    ------------------------------
    Jonathan Siegel
    Director Clinical Statistics
    ------------------------------


  • 2.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-06-2020 06:55
    But isn't any model that leads to unrealistic outcomes (negative death) a priori suspect? After all, resurrection was a one-time historical event. Actually twice, counting Lazarus.

    ------------------------------
    Edzard van Santen
    Professor and Director
    University of Florida IFAS Statistical Consulting Unit
    ------------------------------



  • 3.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-06-2020 08:56
    The "cubic fit" model has appeared in a tweet from the White House Council of Economic Advisers.

    It fairly closely matches Nate Silver's reproduction, except that the White House CEA curve has a taper added and continues past ~May 15 horizontally at zero.



    https://mobile.twitter.com/WhiteHouseCEA/status/1257680258364555264/photo/1

    This explanation, from Carl T. Bergstrom, is the best plain-English explanation I've seen for why the model's extrapolations to the near future may be problematic:



    ------------------------------
    Jonathan Siegel
    Director Clinical Statistics
    ------------------------------



  • 4.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-06-2020 23:40
    If the Washington Post reported it, then I doubt its veracity. They are not the same paper they were in the Nixon years.

    ------------------------------
    Eric Siegel, MS
    Biostatistics Project Manager
    Department of Biostatistics
    Univ. Arkansas Medical Sciences
    ------------------------------



  • 5.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-07-2020 00:03
    The New York Times has also reported on the model and criticism of it. It reports that the model's originator now says that the model was not intended as a forecast.

    No Virus Deaths by Mid-May? White House Economists Say They Didn't Forecast Early End to Fatalities
    Nytimes remove preview
    No Virus Deaths by Mid-May? White House Economists Say They Didn't Forecast Early End to Fatalities
    Mr. Hassett dismissed the criticisms. "It's just silly season," he said. The current acting chairman of the council, Tomas J. Philipson, fired back at Mr. Furman on Twitter late Tuesday evening, mocking his academic publishing credentials, and in a later post, adding a sort of schoolyard-economist's taunt.
    View this on Nytimes >
    L

    ------------------------------
    Jonathan Siegel
    Director Clinical Statistics
    ------------------------------



  • 6.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-07-2020 15:23
    ​Jonathan, I read the New York Times piece and it appears that the angst is premature.  Mr. Hassett mentioned that this was not an attempt to model the virus, but was only a naïve curve fitting exercise with a "cubic polynomial" using Excel, he said further that this plot was not shown to the White House nor the Coronavirus Task Force.  It had nothing to do with policy.  Actually, I would generally consider anything that the CEA produced on Covid-19 to be just an exercise.

    Raoul Burchette
    Biostatistician

    ------------------------------
    Raoul Burchette
    ------------------------------



  • 7.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-07-2020 15:28
    I should add that anything the CEA said concerning Covid-19 as far as medical results (cases and death) I would considered an exercise.​  What they might say about the economic impact of Covid-19 is another story.  If an economic impact report was done by health economists, I would take even more note.

    Raoul

    ------------------------------
    Raoul Burchette
    ------------------------------



  • 8.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-18-2020 08:39
    Completely agree!

    ------------------------------
    Terry Meyer
    ------------------------------



  • 9.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-18-2020 14:02
    One would suppose a "cubic model" implies a 3rd-degree linear function. I suggest a better model would be what has been used successfully for many biological (and economic and other) growth phenomena for two centuries: the asymmetric, double exponential Gompertz curve (B. Gompertz, Phil. Trans. Royal Society, B, 1825). I suspect the SUNS (statistics-using non-statisticians) are not doing diligent groundwork or model testing. However, the media and public, starving for absent information in this data-deficient COVID-19 period, seem willing to accept any prediction, even with the shakiest justification. I'm sure many statisticians (me included with Markov chains) have models that would prove useful if we could just get reliable and appropriate data.

    ------------------------------
    Bob Riffenburgh
    San Diego State University
    ------------------------------



  • 10.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-20-2020 20:29
    I doubt the economist tried to fit probability distribution curves, economists do not usually think that way. They probably looked at year-over-year changes in the aggregate numbers. Whether they tried fitting the cubic to the differences or to the 2 separate years & then subtracting the curves I cannot guess. They only have about 4 or 5 months of comparible data points & they are fitting a cubic so this has got to be iffy no matter how they did it. One possibility is they used the aggregate counts up until March & applied a cubic model to this data to forecast April & then compared the actual counts against the forecasted count.

    ------------------------------
    Jack Lothian
    Senior Survey Methodologist
    Retired
    ------------------------------



  • 11.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-21-2020 06:57
    Andrew Gelman's blog has more detail on this. Apparently, if you add more recent data to it it still fits well to a cubic but it's a different cubic that makes very different predictions. It's just noise and should be ignored.

    Blaise

    Blaise F Egan
    Chartered Statistician



    ------------------------------
    Blaise Egan
    Lead Data Scientist
    British Telecommunications PLC
    ------------------------------



  • 12.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-27-2020 22:12
    I found this thread interesting so I took a shot at curve-fitting using R time-series functions.  Data is from the New York Times github site and runs through May 26 for Covid cases and deaths.  Since this is indeed curve-fitting, I limited myself to 14-day forecasts.  Results show some decline in daily cases and a more marked decline in daily deaths.  This could make some sense in that hospitals may be doing a progressively better job of keeping people alive.  I plan to keep running this script on updated data to see how the trends and forecasts evolve.

    ------------------------------
    Robert Agnew
    ------------------------------

    Attachment(s)

    txt
    COVID.txt   1 KB 1 version


  • 13.  RE: A "cubic model" for COVID-19 deaths

    Posted 05-28-2020 03:10
    Appreciate this.

    An alternative explanation for declining relative death rates might be changes in selection bias. Previously, limited testing capacity meant only people with relatively severe symptoms got selected for testing. But with increased testing capacity, people with milder symptoms are getting tested, along with more asymptomatic people. And perhaps also more false positives. This hypothesis - changes in the set of people selected for testing, not necessarily changes in care - might also explain a decreasing relative death rate.

    ------------------------------
    Jonathan Siegel
    Director Clinical Statistics
    ------------------------------



  • 14.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-01-2020 21:17
    Update.  Using my curve-fitting methodology, daily US Covid case and death trends appear to have bottomed.  New York is headed down after a huge surge.  But other big states are headed up, California in particular.  Bob

    ------------------------------
    Robert Agnew
    ------------------------------



  • 15.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-02-2020 09:33
    Thank you for these analyses. A definite public service and worthy of study. I do want to share a few things about state data:

    After accessing a recent CDC report through the link below, I noticed some alarming inconsistencies in the COVID-19 data reported by Florida. One graph (Figure 1) showed statewide hospital and urgent care discharge diagnosis of influenza (rather than the previously reported COVID 19 as a chief complaint.) At Week 12 there was approximately, 3% discharge of influenza, with the rate plummeting to near 0% for Weeks 14-19. A dramatic decline; a reflection of a sudden cure? There's no reporting of COVID-19, and there's an apparent sense that all influenza has disappeared.

    But, a later graph (Figure 4) showed approximately 375 deaths at Week 12 from influenza, supposedly exclusive of COVID-19, plummeting to about 250 deaths in Weeks 15-17. These data are saying that influenza which can include COVID-19 (but not chiefly COVID-19) has plummeted to 0% at discharge, while there are 250 deaths from influenza that are not associated to COVID-19.

    So, how can the near 0% discharge coincide with 250 deaths? No deaths at the hospital? And the near lack of deaths is for patients not chiefly with COVID-19?  But Figure 4 says there were approximately 250 deaths from influenza without COVID-19. Further, we know that COVID-19 is five to ten times (at least) more lethal than the typical influenza. So, there are inconsistencies between the two graphs, and the graphs are inconsistent with what we know about death rates from the typical influenza vs. death rates from COVID-19. It's likely that the more predominant COVID-19 involved deaths are more likely being counted in the Figure 4 accounting of data, while being ignored in the Figure 1 accounting of data.

    Further, when I clicked on Georgia in the United States map in the CDC link, the message was that I had no access to this "public information".  Another state with questionable counting is Alabama. The Washington Post has reported that in Alabama , if a patient with COVID-19 dies of cardiac arrest, then the patient is not counted as a COVID-19 death. . Question: If someone is hit by a drunk driver and has a heart attack on the way to the hospital in the ambulance, is that death due to the drunk driver. According to the logic of Alabama, and likely Florida, and other states, these deaths are not due to the drunk driver. See how that logic flies in court when there's a trial of the drunk driver.

    Yes, there's a deliberate, dishonest undercount, which is endangering everyone. Further, it's giving many a false sense of security, and given the near incitement by the White House is causing divisiveness rather than cohesiveness in attacking this pandemic.

    See link below.

    Sincerely,

    Mark Y. Czarnolewski, Ph.D. (retired)

    11231 Columbia Pike

    Silver Spring, 20901.

    I got this link for the CDC from Linkedin

    Click on:

    https://bit.ly/2ViFflZ

    Go to : Coronavirus Disease 2019 (COVID-19) Go to U.S. map and click on Florida

    Updated May 15, 2020  Key Updates for Week 19, ending May 9, 2020

    ILI Activity Levels;     Influenza-Like Illness (ILI) Activity Level Indicator Determined by Data Reported to ILINet;    2019-20 Influenza Season Week 19 ending May 09, 2020



    ------------------------------
    Mark Czarnolewski
    ------------------------------



  • 16.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-02-2020 20:57
    Thanks, Mark.  I seem to be having trouble finding those two figures at the CDC site but I had heard about Covid reporting irregularities in Florida and Georgia. https://www.forbes.com/sites/sethcohen/2020/05/22/are-the-test-numbers-right-georgia-florida-and-the-deadly-trend-of-science-suppression/#52f56e5f6009  I was also unable to find usable time-series datasets at CDC, which is why I went to the very accessible NY Times github site.  Despite reporting shenanigans, the daily US case and death trends are up.  And foolish public behavior is likely to accentuate these trends in the weeks and months ahead.  We are very far from being out of the woods in this pandemic.

    ------------------------------
    Robert Agnew
    ------------------------------



  • 17.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-14-2020 20:55
    UPDATE  https://www.raagnew.com/us-covid-monitor.html

    ------------------------------
    Robert Agnew
    ------------------------------



  • 18.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-22-2020 08:31
    UPDATE   https://www.raagnew.com/us-covid-monitor.html

    ------------------------------
    Robert Agnew
    ------------------------------



  • 19.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-02-2020 10:03
    I wonder what will happen to daily US Covid cases 6-to-12 days after the riots started?

    ------------------------------
    Eric Siegel, MS
    Biostatistics Project Manager
    Department of Biostatistics
    Univ. Arkansas Medical Sciences
    ------------------------------



  • 20.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-02-2020 14:11
    Unlike the stock market, it can only go up. If you notice the large entourage surrounding Trump as they walked to the Church, no one was wearing a mask. (You fill in the blank.) Further, when they fired tear gas canisters at the protestors a half hour before the curfew, people and the Church workers were shocked; people started running, rubbing their eyes, taking off their masks,coughing etc. -- all behaviors that increase the chance of transmission to others and vulnerability from others. Obviously, no bother to consult medical expertise in this medically dangerous situation. Not to mention gunfire from other police departments in other localities.

    ------------------------------
    Mark Czarnolewski
    ------------------------------



  • 21.  RE: A "cubic model" for COVID-19 deaths

    Posted 06-03-2020 11:25
    Not to put too fine a point on it, but you should have really been concerned about the protests and not the riots. There are a lot more people protesting than there are rioting. The New York Times published a montage of pictures of both the protests and the riots and the number of people closely packed in many of the protests was quite concerning. But if there is any reassurance, it is that the protests by right wing groups last month did not seem to lead to a surge in COVID-19 cases. Let's hope for the best.

    ------------------------------
    Stephen Simon, blog.pmean.com
    Independent Statistical Consultant
    P. Mean Consulting
    ------------------------------