# Thread: Conditional Probability Problem

1. ## Conditional Probability Problem

A population of voters contains 40% Republicans and 60% Democrats. It is reported that 30% of the Republicans and 70% of the Dems favor an election issue. A person chosen at random from this population is found to favor the issue in question. Find the condition probability that this person is a Democrat.

Thanks for any help

2. Use Bayes' Theorem. Show your work if you are stuck.

3. I don't know how to apply Bayes Rule. Can someone show? I want to use this as an example so I can do my HW problems... Thanks

4. Originally Posted by jzellt
I don't know how to apply Bayes Rule. Can someone show? I want to use this as an example so I can do my HW problems... Thanks
The obvious first step is to introduce notation and define the probabilities:

Pr(R) = 0.4.

Pr(D) = 0.6.

Pr(F | R) = 0.3.

Pr(F | D) = 0.7

The above notation is left for you to figure out. Now, surely you know Bayes Theorem ....?

If you need more help, please show all your work and say where you get stuck.