Originally Posted by

**fixisnotusedyet** Thank you chiro.

A=i am sick

B=i have allele L1

P(A)=10^-7

P(B)=10^-2

We are trying to calculate P(A/B)

P(A/B)=P(A and B)/P(B)=10^2.P(A and B)

But I have no idea how to calculate P(A and B) based on this context.

Based on my sample of only **3 cases**, __observed __P(A and B)=10^-7

I am 100% sure that P(A/B) is somewhere between 0 and 10^-5.

But giving you an answer with an 80% confidence interval... no idea if this is possible

I know the sample is very poor (n=3) but probabilities p and q are so small that I am convinced we can still get something out of this.