Two way table (I think) probability question PLEASE HELP really stuck
Hi I’ve attached the question for reference and also my workings, I’m not sure how to get started as they also tell you about the 18% probability that those who have hepatitis have hepatitis C and I’m not sure how to fit that information into the table. Really appreciate the help.
Original post by katmyster
Clearly you're looking at conditional probablity.
Consider:
What's the standard formula for conditional probability?
How might you fit P( Has Hep.C n Tests +ve) into it? (There are a couple of ways, and one of them uses information you have readily available).
Original post by katmyster
Hi I’ve attached the question for reference and also my workings, I’m not sure how to get started as they also tell you about the 18% probability that those who have hepatitis have hepatitis C and I’m not sure how to fit that information into the table. Really appreciate the help.
If you're familiar with tree diagrams, you may find one of those helpful. The first tier of the tree separates the Hepatitis patients into those who have type C (P = 0.18) and those who do not have type C (P = 0.82). The second tier of the tree then consists of the given test probabilities.
Original post by old_engineer
If you're familiar with tree diagrams, you may find one of those helpful. The first tier of the tree separates the Hepatitis patients into those who have type C (P = 0.18) and those who do not have type C (P = 0.82). The second tier of the tree then consists of the given test probabilities.
Thankyou I got part. A and b now but to do. C) how do you do it?
Original post by katmyster
Thankyou I got part. A and b now but to do. C) how do you do it?
Original post by katmyster
Thankyou I got part. A and b now but to do. C) how do you do it?
For part (c) you must invoke the conditional probability formula, which in general terms is P(A given B) = P(A n B) / P(B).
Original post by old_engineer
For part (c) you must invoke the conditional probability formula, which in general terms is P(A given B) = P(A n B) / P(B).
Okay great Thankyou that’s what i ended up doing
Original post by katmyster
Last question - how do I do part iii)
If we use F to denote forward and S' to denote not Scottish, you're looking for P(F given S'), using the same conditional probability formula as before.
Original post by old_engineer
If we use F to denote forward and S' to denote not Scottish, you're looking for P(F given S'), using the same conditional probability formula as before.
...or, alternatively, given the pool of people we are interested in for part (iii) are non-Scots, you could just eliminate the Scottish column from the table and find P(F).
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