Thread: Probabilities

Okay I have an answer for this one, but it just seems to easy , Can somone tell me if I did this right. I feel like theres more to solving the problem then what I did. Heres the problem:


The table below gives the probabilities of combinations of religion and political parties in a major U.S city.



Political parites Protestant (A) Catholic (B) Jewish (C) Other(D)

Democrat (E) .35 .10 .03 .02

Republican ( F) .27 .09 .02 .01

Independent (G) .05 .03 .03 .01


What is the probability that a randomly selected person would be a democrat who was not jewish?


The probability I got was .47, all I did was p(.35)+p(.10)+p(.02)= .47
but it just seems to easy.

Originally Posted by jax760

Okay I have an answer for this one, but it just seems to easy , Can somone tell me if I did this right. I feel like theres more to solving the problem then what I did. Heres the problem:


The table below gives the probabilities of combinations of religion and political parties in a major U.S city.



Political parites Protestant (A) Catholic (B) Jewish (C) Other(D)

Democrat (E) .35 .10 .03 .02

Republican ( F) .27 .09 .02 .01

Independent (G) .05 .03 .03 .01


What is the probability that a randomly selected person would be a democrat who was not jewish?


The probability I got was .47, all I did was p(.35)+p(.10)+p(.02)= .47
but it just seems to easy.

You need the concept of conditional probability: .

Now substitute the data (you have already unwittingly calculated the numerator: 0.47).


Edit: NO you don't. Your answer is correct. Conditional probability is not relevant in this question.

Originally Posted by mr fantastic

You need the concept of conditional probability: .

Now substitute the data (you have already unwittingly calculated the numerator: 0.47).

I guess it's matter of interpretation, but it seems to me the question asks for , in which case the answer given in the OP is correct.

Originally Posted by awkward

I guess it's matter of interpretation, but it seems to me the question asks for , in which case the answer given in the OP is correct.

I agree completely with that.
What would your answer be if the question were “What is the probability that a randomly selected person is a Jewish Democrat?”

Originally Posted by Plato

I agree completely with that.
What would your answer be if the question were “What is the probability that a randomly selected person is a Jewish Democrat?”

.

Originally Posted by awkward

.

Again I agree with you. I agreed with you the first time that the OP is correct.
I don't see anything Bayesian about this.

Originally Posted by Plato

Again I agree with you. I agreed with you the first time that the OP is correct.
I don't see anything Bayesian about this.

Both you guys are right. My mistake.