It's used as a mantra because it's a truism. Truisms have truth on their side, however meaningless they may be. So we must point out why they are true. In this case, it's because there could be confounding factors - other causes. So we need to find out what all the causes of all the events are, to get at the truth. Until we are able to do so, we can only hypothesise with the objective of forming theories. This is a valid part of a scientific process.
I fully agree. It is interesting, though, that this "truism" wasn't quite respected for 1,5 year with regards to so called "COVID deaths" and "COVID infections" whatsoever. As any undergraduate statistics student should know slight error margin in specificity translates to huge false positive rate when prevalence is very low: including period when disease barely reached Europe and season wears off. Yet, official numbers didn't reflect that at all.
So know we have ppl outraged that skeptics don't believe "official" numbers even though officials demonstrated no respect for mathematical "truisms" repeatedly. Where is logic in that?
False positive rate (FPR) is a function of the test. It is not related to the prevalence of the virus.
It is defined as FP/N ; where N is all negatives (TN+FP)
You can learn all about it here..
