Different tests have different false negative rates. Elon was using antibody tests which are faster at producing results but have higher inaccuracy.
Futhermore it makes sense that there an amount of antibodies in the body where 50% of the tests you do pass the tests nearly regardless of the quality of the antibody tests.
An antibody test gives a scalar value of how much antibodies there are. If you want to go from a scalar value to a binary value you have to decide on a cutoff that switches from infected to -not-infected.
Given even a tiny bit of test inaccuracy, when the amount of antibody reaction is right at your cutoff, you will have 50% showing infected and 50% showing not not-infected.
Different tests have different false negative rates. Elon was using antibody tests which are faster at producing results but have higher inaccuracy.
Futhermore it makes sense that there an amount of antibodies in the body where 50% of the tests you do pass the tests nearly regardless of the quality of the antibody tests.
I don’t understand the last paragraph. How does that work? Feel free to reply with a link to something if it’s too long to explain.
An antibody test gives a scalar value of how much antibodies there are. If you want to go from a scalar value to a binary value you have to decide on a cutoff that switches from infected to -not-infected.
Given even a tiny bit of test inaccuracy, when the amount of antibody reaction is right at your cutoff, you will have 50% showing infected and 50% showing not not-infected.
Got it, thank you!