5 ms·
> Why would you want to control a system with 2-3 weeks of additional lag in your input data when case numbers (a thing that is somewhat easy to measure) correl
by freeflight 5y ago
> Why would you want to control a system with 2-3 weeks of additional lag in your input data when case numbers (a thing that is somewhat easy to measure) correlates so well future deaths?
Because case numbers are actually not easy to measure.
I'm basing this of my personal experience working in a German healthcare company, we took up testing during the pandemic; All the tests we do are on unvaccinated people.
That's because unvaccinated people are the only ones who need mandatory, and up to date, tests for pretty much everything from the barber to eating at a restaurant. Recently, it's become so strict that unvaccinated people even need a test to use public transport.
Vaccinated people do not need these mandatory tests, I have no clue who tests them and at what intervals, it certainly ain't the public testing stations, as those are now literally swarmed by the unvaccinated and nobody would go there if they didn't have to.
Which means that in practice we have a massive sampling bias going on; Somebody who's unvaccinated will be very likely to get flagged as positive very quickly, while somebody who's vaccinated would need to decide on their own to do a test.
- makomk 5y agoThe obvious solution to this problem is to do actual random sampling: pick members of the public in as close to a random fashion as possible, test them for Covid regardless of vaccination status or symptoms, and you should be able to get a reasonably unbiased estimate of actual infection levels in the community. The UK has been doing this since about spring 2020, but weirdly no-one else seems to even though it's obviously useful.
- freemint 5y agoJust doing random sampling on a small group to estimate the error ratio should also work. Also as long as everyone who has symptoms can get a test the error ratio is bounded by the ratio of people with symptoms making it irrelevant for this control problem.
- freemint 5y agoBetter is the worst enemy of good. Please suggest a different metric then. One that can be measured easily and will do about as well as the biased infected numbers or one which will do better than the biased infected numbers at a similar effort. There is little control theoretic relevance of the Dunkelziffer smoothly varying between 2 and 6 as long as that doesn't make the controller overlook a wave (it doesn't). The sign of the policy should still be the same and if measures don't work, harder measures are imposed means we basically got a PI(D) controller and can achieve stationary solutions even if the Dunkelziffer changes smoothly.
- hef19898 5y agoSure, there is selection bias. Given the overall effectivness of vaccines, the number of positive, yet untested, vaccinated people should be rather small. Plus, those vaccinated without symptoms most likely are not the problem as they are not really infectious. Once you develop symptoms you are tested. On tip of that, a lot of states are now on 2G+, recovered or vaccinated and tested (anti-gen), for things like cinemas (requiring official tests in e.g. Bavaria) or self tests on site (fitness studios for example). Kids are regularly tested in school (my son three times, my daughter twice). Sure, some of those tests, those at fitness studios, are not counted. If those are positive, I think the number of people not getting a proper PCR test is rather small.
- microtherion 5y agoI'm sure you're right regarding sampling bias, but the vaccinated people I know have not turned off their phone contact tracing alerts, and get tested if they receive a tracing notice.
- spurgu 5y agoPeople get tracing alerts? I've had the apps of three different countries now for some 1.5 years running now and never received even a single blip.