# Probability Q

How do you answer this question? --------- In Favour Against CFA Charterholders --------- 235 765 CFA Candidates --------- 180 820 Given the information that a member of the group is in favour of a continuing education requirement, what is the probability that she is a CFA Candidate? A) 37% B) 43% C) 50% D) 57%

B

Identify group Identify the sub group Do the maths Getter done is right

total charter holder = 1000 total candidates = 1000 total favors = 415 235/415 =D

How do you do this can you please throw light P(she is charterholder | all people who favor the program) = P(she is charterholder and favors the program) P(ppl who favor the program) so (235/415)*415/2000

You just did it above and then changed your correct answer…

so joey you say the answer is D?

The answer is A) 37%. Not sure how.

would love to know how, dont see how this is possible

It’s 180/(180 + 235) whatever that is.

thats b but they say the answer is A what the FUDGE is up with this Q

this is crap i read the damn hting wrong. its 180

getterdone Wrote: ------------------------------------------------------- > thats b but they say the answer is A > > what the FUDGE is up with this Q They’re wrong.

I get B as well. WFT!!

I draw my tree and it is B. I don’t see A. Total population: 2,000 CFA charterholders: 1000 that’s 50%. Say YES, in favor: 23.5% of them Say NO, against: 76.5% of them CFA candidates: 1000 that’s 50%. Say YES, in favor: 18% of them Say NO, against: 82% of them P(CFA candidate|YES)=P(YES|CFA Candidate)*P(CFA candidate)/(P(YES) = 18%*50%/(18%*50%+23.5%*50%) = 43.37%~43%

thats how I did it

yeah tree gives answer B

are you using Bayes formula after you draw the tree. I draw the tree too but I become unsure how to apply the information in tree to the question.

You don’t need Bayes here. 415 people are in favor. 180 of them are candidates. 180/415 problem solved.

pepp joey is right, you don’t really need the formula here but since i already took the 2 minutes to draw it out, here is how you would apply it if a problem did require the tree http://i28.tinypic.com/2lvbsd2.jpg