I have been wondering about an issue connected with prevalence. And came up to some conclusions which I would like to verify. It's not complicated. Let's assume we have two prevalences: (A) percentage of population with cancer - 10% and (B) population of smokers - 20%. If there would be no correlation: C = 0, the populatin smokers with cancer (D) would be D = AB = 2%. If The correlation would be C = 100% then everyone with cancer would be a smoker - D = A = 10%. So the correlation proportion wolud be:
50% ((A or B) - AB)/2
F% ((A or B) - AB)*F/100
100% if A < B then A, if A > B then B
Is this right?
Thank you in adv,