Can we give @DHSCgovuk and @educationgovuk a lesson in probablilty? This is A level stuff - if there are Year 12 and 13s in isolation please try it (you can do it with Venn diagrams or a Tree diagram) and send your full workings to @GavinWilliamson @MattHancock @SMHopkins
(a) In 1,000,000 children of which 0.1% have Covid-19, if a test gives +ve results with probability 0.5 in those with Covid-19 and -ve results with probability 0.999 in those without, how many +ve results would you get, and how many of these would actually have Covid-19?
For Further Maths geeks:
(b) If those +ve on the first test and tested with a second test which gave -ve results in those without disease with probability 0.990, how many will not have Covid-19 infection AND have a +ve result on the 1st test AND have a +ve result on the 2nd test?
(b) If those +ve on the first test and tested with a second test which gave -ve results in those without disease with probability 0.990, how many will not have Covid-19 infection AND have a +ve result on the 1st test AND have a +ve result on the 2nd test?
Answers
(a)1,499 positive results, 500 with Covid
(b)10.
(a)1,499 positive results, 500 with Covid
(b)10.
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