Does Faire actually have COVID after testing positive with mild cold-like symptoms?
82%
chance
May 19
M$621 bet
She woke up with a slight sore throat and took two rapid tests in a row, both positive. Later she developed a slightly runny nose and very occasional cough. Twist: See this market: https://manifold.markets/dreev/do-i-have-covid-despite-testing-neg
dreev

Daniel Reeves is betting NO at 48% 13 days ago

Auxiliary market for the preceding question: https://manifold.markets/dreev/does-a-vaccinated-person-with-mild
dreev

Daniel Reeves is betting NO at 48% 13 days ago

I suppose if we assume Faire and I have the same virus then our results are kind of like if you got some mild symptoms and took 4 tests in a row and 2 were positive and 2 were negative. How would you Bayesian-update on that?
dreev

Daniel Reeves is betting NO at 48% 13 days ago

If we ignore the fact that Faire and I probably have the same virus and just naively apply Bayes' rule for each of us, starting with some prior of having Covid given our symptoms and using the sensitivity/specificity in the pamphlet, we get this for posterior probability as a function of prior probability (blue line is positive test, orange line is negative): https://user-images.githubusercontent.com/9928/168338624-1df49a71-a594-44ff-abbe-d00b2290af96.png So, like, if you got a scratchy throat and slight cough and runny nose and were like "this seems like a 20% chance I have covid" and then you took a rapid test... * if it says positive (like for Faire) then you go from a 20% chance to a 92% chance * if it says negative (like for me) then you go from a 20% chance to a 1.4% chance
dreev

Daniel Reeves is betting NO at 48% 13 days ago

Update today: I still have a mild cough but getting better and otherwise feel fine. Faire has been totally fine for days now (today is day 5 for her, with her positive test Sunday being day 0).
dreev

Daniel Reeves is betting NO at 48% 13 days ago

I just took another test as well (about 24 hours later) and still negative! My symptoms today: sore throat gone, cough worse (but still not bad), ever so slightly headachy I guess but mostly pretty normal. Runny nose pretty much better, but was only ever very minor. I'm day 2 or 3. (Tuesday I had an inkling I was getting sick, Wednesday was the first day of actual symptoms, though still very mild.)
dreev

Daniel Reeves bought M$88 of NO13 days ago

The antigen rapid test pamphlet says sensitivity ie Pr(pos | covid with symptoms) = 33/35 and specificity ie Pr(neg | not covid but yes symptoms) = 102/104
brp

brp is betting YES at 48% 13 days ago

@dreev These numbers aren't enough to derive anything solid about your position, but having reviewed https://www.lesswrong.com/posts/cEohkb9mqbc3JwSLW/how-much-should-you-update-on-a-covid-test-result, I think I invested *much* too aggressively.
dreev

Daniel Reeves is betting NO at 48% 13 days ago

@brp Ah, thanks for that link! We're using the "iHealth COVID-19 Antigen Rapid Test" which isn't mentioned there. And of course the other confusing monkey wrench in our calculation is Faire testing positive but me testing negative with the same symptoms.
jack

Jack 12 days ago

@dreev I'd probably use the average stats for all rapid tests, I suspect that most rapid tests are in the same rough ballpark. I also commented on the other market about this https://manifold.markets/dreev/does-a-vaccinated-person-with-mild - you should ignore the pamphlet stats, apparently they are completely bogus because the sample for them is highly infectious individuals (chosen to make the statistics pass arbitrary regulatory standards) - that's why it comes out with such a high sensitivity rate compared to the meta-review.
dreev

Daniel Reeves is betting NO at 93% 13 days ago

Ha, Faire just took another test, day 4, and it's negative!
brp

brp is betting YES at 48% 13 days ago

@dreev Good for her! I hope it's just allergies, but I still kind of doubt it..
dreev

Daniel Reeves 14 days ago

Very good question. It's entirely possible we won't get a definitive answer and will have to resolve it as either "N/A" or resolve to the market's own probability. We can commit to updating this thread with all the new information we have.
brp

brp bought M$100 of YES14 days ago

How does this market resolve? A PCR test? More rapid tests? Worse symptoms?