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Preliminary test results suggest 21% of NYC residents have Covid antibodies

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Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#551

Post by s1artibartfast »

GhostVII wrote: post #486
Uhhrrr wrote: post #468

Earlier quoted context omitted.

It will probably be significantly higher than 60%, since COVID-19's R0 without lockdown seems to be pretty high. The CDC has estimated it at 5.7 [0]. Herd immunity threshold = 1 - 1/R0, so the threshold would be 82.4%. [0] https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article?deliv...

That R0 assumes we are taking essentially no measures to stop the virus though, right? I don't no much about it but it seems like the R0 would drop significantly if we keep doing social distancing, expand testing, make people wear masks, etc.

The 5.7 number comes from wuhan, during lunar new year, and before viral identification.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#552

Post by hkai »

Aha! So perhaps we shouldn't have shut down the economy and financially ruined millions of people, not to mention the hundreds of millions of people on the brink of starvation in developing countries.

Perhaps we just like sharing images of coffins and feeling virtuous.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#553

Post by SerLava »

hkai wrote: post #552

Aha! So perhaps we shouldn't have shut down the economy and financially ruined millions of people, not to mention the hundreds of millions of people on the brink of starvation in developing countries. Perhaps we just like sharing images of coffins and feeling virtuous.

Even if the study is true, this doesn't follow.

You only get to limit your response if you have the capability to do actual testing... which we didn't and still largely don't.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#554

Post by cco »

iso947 wrote: post #469
hcknwscommenter wrote: post #349

Earlier quoted context omitted.

It is very positive in that we can be more confident that our assumptions are close to reality. 0.5%*330M still equals 1.65M deaths, or (very roughly) 5M ICU beds. Spread out over 52 weeks, that's a lot of ventilators and ICU beds and PPE, but it is a target. A very big juicy target that we can and should aim directly at, and HIT.

So having killed 1.6 million in the US alone and run ICU at 100% for a year, you’re just going to hope people remain immune and the virus doesn’t mutate having passed through billions of people worldwide?

The alternative being...? We know that covid-19 will likely mutate, just like other coronaviruses, H1N1 and its mutations are still around every year; are you suggesting we must remain in quarantine until we both create a vaccine for covid-19 and then every fall quarantine until we're able to develop a vaccine for that year's bout of viruses?

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#555

Post by Dylan16807 »

godelski wrote: post #393
dragonwriter wrote: post #298

Earlier quoted context omitted.

> Why does recruiting through Facebook invalidate the results? If Because “people who both use Facebook and don't automatically discount every ad or other solicitation on Facebook not from someone they personally know, especially if it invokes a major news story, because of the risk of it being a scam looking to steal personal information or do something similarly nefarious” are not representative of “people”.

If a representative portion of the population didn't click on Facebook ads then Facebook wouldn't generate revenue from these ads. Testing doesn't rely on the person being intelligent either. Because it sounds like you're just saying "results are bad because only idiots would click on a Facebook ad".

> If a representative portion of the population didn't click on Facebook ads then Facebook wouldn't generate revenue from these ads.

That doesn't make any sense. Ads can make plenty of money even if they're only seen by women, or people between the ages of 30 and 70, or people in zip codes divisible by 3.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#556

Post by capkutay »

aazaa wrote: post #317

> In his press conference today, Governor Cuomo revealed the preliminary results of a first-phase antibody test that surveyed 3,000 New Yorkers over two days in 19 counties at 40 locations that included grocery and big-box stores. The sample suggests that 13.9% of New York State residents have the antibodies, meaning they had the virus at one point and recovered. Of the regions tested–Long Island, NYC, Westchester/Ro…

> This still is not a random sampling. It only samples from shoppers at grocery stores and big-box retailers. Imagine doing the same study, but of people who ordered groceries online only. Would you expect to see big differences in exposure rate? I think so.

I'd expect people who still do their own grocery shopping and go to big box retailers to be a better sample of the population than hacker news' audience definition (ordering from instacart/whole foods, working on Zoom/slack all day).

The vast majority of the population does not have the privilege that many people in the tech industry do. Going to a grocery store is a pretty basic activity in most of the population. People who get their groceries delivered online and can maintain their livelihood being on Zoom calls all day are probably statistically insignificant enough to be covered in the sampling error.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#557

Post by ineedasername »

ineedasername wrote: post #332
austingulati wrote: post #221

Earlier quoted context omitted.

Wouldn't the ability to refuse taking the test introduce bias? i.e. the 10% that do take it still may not be representative of the entire population. Likely better than the grocery store sample, but still not ideal

Sure, phone surveys for political purposes (presidential approval ratings etc.) have to deal with that all of the time. There are methods for estimating non-response impact. [0] One method of mitigating it that I've seen it to reach out again to non-responders. You then analyze their results to see how they differ from the baseline responders to estimate the non-responder population. If there's little/no difference,…

Wow, downvoted for providing factual information on how researchers mitigate non-response bias. Didn't think there was anything controversial there. I'm willing to accept the additional downvoted for this comment though.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#558

Post by capkutay »

Karrot_Kream wrote: post #401
TheBlight wrote: post #348

Earlier quoted context omitted.

Sure all of these studies are potentially flawed but they're all generally pointing in the same direction. There are many more infections than we know about and the CFR is not anywhere close to the actual IFR. NYC is an outlier with a 21% infection estimate but for the rest of NY (outside NYC metro/Westchester/LI) the estimate is 3.6%. Santa Clara estimate was 3%. LA County estimate was 4%. Seems like a trend is deve…

> Sure all of these studies are potentially flawed but they're all generally pointing in the same direction That's unfortunately not the way statistics works. Combining multiple bad tests just makes the results incorrect or highly uncertain; the devil often is in the details. The Stanford/Santa Clara County study is a good example of how the details can really undermine a study. Things do indeed seem to be converging…

OP's whole point is it's not a good sample because people were recruited while grocery shopping...I can't think of a more tech industry-oriented view of the world; most people work from home on zoom and use instacart right??

No. I'd expect people who order deliveries online and can do their entire job on Zoom/slack all day to be a minority to the point where including them in the study would be covered in a sampling error.

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#559

Post by qqqwerty »

akiselev wrote: post #539
CydeWeys wrote: post #433

Earlier quoted context omitted.

The study is dramatically over-sampling exactly the people who have the most potential exposure to COVID-19, and dramatically over-sampling the people who don't. This could easily be way off. It's not testing the people who aren't home at all, and it has a low chance of only testing the people who leave home rarely, only when strictly necessary. It's mainly finding the people who leave home a lot.

Couldn't you get a bad study that reverses the sampling bias to get a decent picture of social distancing strategies using the two bad studies? That alone seems far more useful than knowing the IFR because its actionable information.

Or better yet, do a simple survey and ask the participants how frequently they go to the grocery store. And if you see a correlation between frequency and infection rate, then try and adjust your weights accordingly.

These bias issues are well known among survey designers. There are ways that you can try and account for them. It seems like maybe the medical community is too used to having control groups in their studies?

Re: Preliminary test results suggest 21% of NYC residents have Covid antibodies

#560

Post by ineedasername »

greedo wrote: post #501
ineedasername wrote: post #310

Earlier quoted context omitted.

Flu rates are based on all known knowledge, population testing, etc. We don't have that for covid-19. If you want a good apple-to-apples comparison of lethality of another pandemic, you need to find CFR numbers that were available during the pandemic. That is what I provided in my post. Here is the source I got them from [0] which gives the CFR at the 10-week mark for H1N1, somewhat similar to where we are now. Here'…

The amount of testing for influenza is nugatory. Most of the CDC data is collected by surveys, not tests.

There are near instant tests for flue in most every urgent care center I've been to (easier and faster than getting a dr appt.)

Whenever I have gone or brought my kids when sick, they perform the test to rule out any potential need for antibiotics. When I asked, they said it's systematically reported to the the CDC as part of their flu surveillance system, whether positive or negative. That surveillance network is significantly more robust than a survey.

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