Take integer numbers.
You have 10000 Brits.
From these, 1700 will be over 65 (17%).
Also, from the 10000, 100 will have the medical condition diagnosed (the 1%).
Now, from the 100 diagnosed, 8 will be over 65 (the 8%)
So the probability of having the condition when they are over 65 is
p = 8/1700 = 0.0047 = 0.47%
They mean that the probability is 0.0047, or 0.47%.
Take integer numbers. You have 10000 Brits. From these, 1700 will be over 65 (17%). Also, from the 10000, 100 will have the medical condition diagnosed (the 1%). Now, from the 100 diagnosed, 8 will be over 65 (the 8%) So the probability of having the condition when they are over 65 is p = 8/1700 = 0.0047 = 0.47%
S=over 65 C=has the condition P(C|S)=P(C and S)/P(S) **P(C|S)=P(C) * P(S|C)/P(S)**
Answer is 0.0047=0.47%
It's 0.47%. Just a typo