I don't know what to make of that. I would expect people at work to have higher infection rate (not the least because many of these jobs involve contact with the population). It also filters out older and sick people. So intuitively I would expect to undershoot the actual rate.
I read it as people shopping, not people that work there. So folks who are out-and-about, but are not in the more likely to have it groups (healthcare workers or people working at the grocery store). You're right about older and sick people.
No that's what I meant. People shopping and therefore not at work. Therefore intuitively I would expect the population tested to be less contaminated than the population not tested (because at work).
