[heartwood]

The people getting sampled for antibodies are from that fraction who can be found out at the store.

There are plenty more old and vulnerable who don’t come out at all.

The sample is not fully representative of the population.

[Raycpa]

The people getting sampled for antibodies are from that fraction who can be found out at the store.

It could be representative. My 89 father and 87 year old mother venture out on shopping trips about once every ten days. (No, I can't stop them) If others are like them, then the population they tested includes high risk folks.

[FreeReign]

The people getting sampled for antibodies are from that fraction who can be found out at the store.

The number of people who are homebound or hospital bound are less than 1% of the population. Everybody else potentially goes to the food store.