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Unformatted text preview: STAT 100A HWI Due next Wed in class
Problem 1: Suppose we ﬂip a fair coin 4 times independently. (1) What is the sample space? (2) What is the set that corresponds to the event that the number of heads is 2? What is its probability? (3) Let Zi = 1 if the i-th ﬂip is head, and Zi = 0 otherwise, for i = 1, 2, 3, 4. Let X be the number of heads. Express X in terms of Zi . (4) What is the probability distribution of X ? That is, what is Pr(X = k ) for k = 0, 1, 2, 3, 4? Problem 2: Suppose we roll a fair die twice independently. Let X and Y be the two numbers we get. (1) What is the sample space? Let A be the event that X > 4, and B be the event that Y > 4. What are Pr(A), Pr(B )? (2) Let C be the event that min(X, Y ) > 4? What is Pr(C )? What is the relationship between Pr(C ) and Pr(A), Pr(B )? (3) Let D be the event that max(X, Y ) > 4? What is Pr(D)? What is the relationship between Pr(D) and Pr(A), Pr(B ), Pr(C )? (4) If I tell you that X > 4, what is the probability that X = 6? (5) Let Z = X + Y , what is the probability distribution of Z ? That is, what is Pr(Z = k ), where k goes through all the possible values that Z can take? Problem 3: Suppose we draw two random numbers uniformly and independently from [0, 1]. Let X and Y be the two numbers. (1) What is Pr(.1 ≤ X ≤ .4)? In general, for A ⊂ [0, 1], what is Pr(X ∈ A)? (2) What is Pr(X + Y > 1.5)? (3) Let A be X < .3, and let B be Y > .6, what is Pr(A ∩ B )? What is the relationship between Pr(A ∩ B ) and Pr(A), Pr(B )? (4) What is Pr(X 2 + Y 2 > 1)? (5) Suppose I tell you X + Y > 1, what is the probability that X > 1/2? 1 ...
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This note was uploaded on 04/09/2009 for the course STATS 100A taught by Professor Wu during the Fall '07 term at UCLA.
- Fall '07