This means that, on average, Apple Watches will be wrong more than 80% of the time
Sound counterintuitive? This is the issue with population screening
The population prevalence for atrial fibrillation is about 1%
So, in the remaining 990 people who are tested, 40 will receive positive results
Some of them will probably die
Even if your test is FANTASTIC, you have to be really damn careful
Because otherwise you can KILL PEOPLE
Serves me right for being overconfident!
The true negative identification should be 4, thus the watch is only wrong ~1/3 of the time
Still a fascinating phenomenon
For example, if 10% of the population have AF, then the watch only gets it wrong a tiny percentage of the time