Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
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Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#2If the R0 is truly near six, we have probably climbed near the top of the S curve already all over the place. We will know in a month.
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#3Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#4So halfway to herd immunity?
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#5> The 200 participants generally appeared healthy, but about half told the doctors they had had at least one symptom of COVID-19 in the past four weeks.
The total sample size is small and this doesn't seem random enough?
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#6A third of a random sample taken in Chelsea, Massachusetts:
https://en.wikipedia.org/wiki/Chelsea,_Massachusetts
>Chelsea is [...] directly across the Mystic River from the city of Boston. [...] It is also the second most densely populated city in Massachusetts behind Somerville.
A random sample in a highly affected and extremely dense area is not a model for the whole state.
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#7Hmm, I wonder if they attempt to control for bias. It sounds as though they were asking random passersby if they wanted a COVID-19 antibody test. If so, it seems that the sample group could be biased toward including more people who suspected that they may have been infected (previously or currently) than a truly random sample.
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#8So halfway to herd immunity?
Go Cows!
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#9> The 200 participants generally appeared healthy, but about half told the doctors they had had at least one symptom of COVID-19 in the past four weeks. The total sample size is small and this doesn't seem random enough?
You should be much more worried about bias than about sample size. See also this calculation, where it is discussed that a sample of 400 is more reliable than a slightly biased sample of a million participants:
https://marginalrevolution.com/marginalrevolution/2020/01/bi...
Re: Nearly a third of blood samples taken in Chelsea show exposure to coronavirus
#10>Nearly one third of 200 Chelsea residents who gave a drop of blood to researchers on the street this week tested positive for antibodies linked to COVID-19, a startling indication of how widespread infections have been in the densely populated city.
>The doctors used a diagnostic device made by BioMedomics, of Morrisville, N.C., to analyze drops of blood. It resembled an over-the-counter pregnancy test and generated results on the street in about 10 minutes.
This is the only recent testing I've seen that appears to be anything remotely resembling random. The sample size is also not incredibly small. That said, this is the first I've heard that there's a handheld device which can deliver an antibody test in 10 minutes and being completely out of that industry I have to wonder how likely it is that it's delivering a high level of false-positives?