### CFA Practice Question

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### CFA Practice Question

A jar contains 3 red and 5 yellow balls; two balls are randomly selected from the jar. Which of the following is true?

A. This is a binomial situation.
B. The events first pick and second pick are independent events.
C. P(red ball and yellow ball) = 0
D. The events first pick and second pick are dependent events.

User Comment
surob Why?
Mattik Because on pick 1:

P(red) = 3/8 and P(yellow) = 5/8

Now, if on pick one you get red, then

On pick 2:

P(red) = 2/7 and P(yellow) = 5/7

therefore, Pick 1 "affected" pick 2 and they are dependent.

If, on the otherhand, the ball chosen on pick 1 were replaced, then pick 1 and pick 2 would be independent (because picking either color on pick 1, would NOT change the P's on pick 2)
coolnan Thanks-Mattik.
Mikael I could not understand why A was not correct. I think this is because the two trials are not independent. So, p cannot be constant (as required by the binomial distribution).
NikolaZ How are these dependent events, and on the previous question when drawing a Queen and then a heart/diamond are independent events?
Seancfa1 NikolaZ, because in this situation you have 2 occurrences of the event, whereas in the Queen vs Heart/Diamond you had only 1 occurrence. If there were multiple occurrences of the Queen vs Heart/Diamond situation it would be a dependent series of probabilities.
Shaan23 Mikael - I dont understand why this is not binomial either. If you were to ask me what is the probility of getting 2 R's I would do 8C2 with p=3/8....a binomial distribution quesiton