Group testing

Christian Gollier and Olivier Gossner pass on a beautiful and simple idea: Group testing. (They sent slides by email, I'll add a link when I get one.)

To stop the virus, we need testing. But we don't have enough tests. As a result, a trillion dollars a month stands to go down the toilet, unemployment is skyrocketing, and a big financial crisis looms. What to do?

Test groups. Group testing works particularly well given that so far, the percentage of infected people is low.

Get a group of 32 people, and they each spit in a bucket. Test the bucket. (Metaphorically. Actually, mix their samples.) If it's negative, everyone in the group is clean and they can go back to work.

If not, split into two groups of 16, and test again. Again, if a group of 16 is negative, they're all clear. Keep going 8, 4, 2, 1

If nobody has it, you find out in 1 test, not 32. If 1 out of the 32 has it, you find him or her with 12 tests not 32.

Often the goal of testing is not to find one particular person. And if tests take a day to come back, repeated testing is impractical. But with two rounds of testing you can at least very quickly find groups of 32 and 16 who are all clear, and isolate the smaller groups.

This idea strikes me as particularly good because of the spatial concentration of a virus. With one test we can find out if a city of 10,000 has any infected people. With one test, we can find out if a zip code is free of virus.


from The Grumpy Economist https://ift.tt/3dzKE0e