statistics: Distribution and Expectation

dhs316

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Jan 27, 2010
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Questions 17 - 20 refer to the following: a bowl contains 2 red chips and 2 white chips. Two
chips are withdrawn at random simultaneously. Y is the number of red chips among them.
17. What is P(Y = 2)?
18. What is the mean u of Y ?
19. What is the variance sigma^2 of Y ?
20. What is E [(Y + 2)2]?

17.)(2/4)(1/3) = 1/6
18.) (0+1+2)/3 = 1
19.) The answer is 1/3. I don't how that was reached. I know x^2f(x)+u^2 = 5/3-1^2 =2/3.
20.) =EY^2+4EY+4

Can someone check my logic for 17 and 18? Also, can someone show me how to do 19 and 20 correctly. Thanks.
 
I still need help. I dont understand mean and variance in the context of picking chips. For 18, I got (0+1+2)/3 = 1, but for B (0^2+1^2+2^2)/3 -1 gives 2/3, which is not 1/3. SO i think my method is wrong. Please help me get the correct method. Thanks
 
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