@EducatingArti
There seems to be an increasing amount of activity on Twitter from those who feel that the whole virus is some kind of hoax to restrict individual liberty.
Their arguments seem to centre around the false positives, eg there are 8 false positives for every one case.
Can anyone explain clearly why this false positive argument is flawed as I'm struggling to put it all together right now.
....
The false positives matter if a population is being tested
completely at random during very low infection levels
However, when people are being tested for symptoms, or close contact, then false positives are a far smaller %,
especially when infections are rising
This false positive argument was started by the irresponsible Julia Hartley-Brewer
- who has an ideological agenda and an insatiable desire for publicity, so always looking to stir
She asked David Spiegelhalter the consequences of a 0.8% FPR (False Positive Rate) which had been stated by Hancock on air
and then she misused the answer for mass testing & ignoring his later post on testing with symptoms
As we've discussed before,
the false positive % has very different consequences for random mass population testing vs testing of people with symptoms or their family members
The claim that therefore the rise in infections is fake also ignores the 30% or so of false negatives
If you want to rebut the 91% false claims, then you could copy both Spiegelhalter's tweets on the topic:
David Spiegelhalter @dspiegel
Tweet below is for mass testing.
Very different if test 1000 people with symptoms
then from PHE data expect 40-50 covid, detect say 30-40.
So most positive tests are correct.
The current rise is real.
David Spiegelhalter @dspiegel
Replying to @JuliaHB1
If you test 1000 people at random, latest ONS figures estimate 1 will have the virus, and let’s assume you find them.
But with an FPR of 0.8%, that’s 8/1000, and so you expect to find 8 false positives.
That’s 9 positive tests, only one of which has the virus