I need help on understanding the question for probability trees

I understand all the fundamentals of probability trees I just struggle to draw the trees from what is given in the question.

Welcome @angie!

To convert a statement into a mathematical model is a hard task indeed.

Lets consider example. 3% of population get flu. The probability of false positive test is 10% and the probability of false negative test is 1%. You need to draw a probability tree.

Firstly, you have to determine order of the events. Event 1 would be getting flu (3%) or not getting flu (97%). Make sure that probabilities of the branches add up to 100%.

Then you need to list outcomes for each branch. Out of those who got sick 99% had positive test and 1% negative. Out of those who didn’t get flu 10% recieved positive test and 90% - negative test result.Flu

If you send specific questions you have troubles with we will be able to assist you better.