The gist of it
Though there are many types of Covid tests, I think none have 100% sensitivity or specificity. What I would like to know is if the event of getting, e.g., a false negative on two tests are independent events.
Suppose I take two samples from the same person in rapid succession (not on consecutive days but 1 minute apart) and run the same type of test on each sample. Is it possible to have one test come back negative and the other positive, assuming the samples are not contaminated and the tests were run properly?
Basically I would like to know if the randomness occurs in the biology of the person, at sampling, or in the biochemical analysis phase of testing.
Perhaps the answer may vary depending on the type of test. (I am also curious about tests for other diseases, but I guess that would make the question too broad.)
I read the CDC's Testing Overview, and several questions on this SE, e.g.,
Do having multiple COVID tests decrease the chance of a false negative?
How accurate are coronavirus tests?
What is the expected false positives/negatives for COVID-19 tests?
and also at Biology
What's happening in the “C” and “T” stripes of a covid test kit?
but found no answers. (There was a vague statement in a comment but no reference or explanation was given.)