I guess my question would be, "Out of positive test cases, what fraction sought testing because of symptoms?" For random tests, I would guess that the positivit

I guess my question would be, "Out of positive test cases, what fraction sought testing because of symptoms?" For random tests, I would guess that the positivity rate is far, far lower than for folks seeking tests due to symptoms. Therefore, I expect that folks seeking tests due to symptoms are the large majority of the positive tests. I cannot submit any proof of this view, but it is what seems most likely to me.