SOLUTION: suppose you will be taking exams in english, chemistry and statistics tomorrow. further, you know from past experience that you have a 50% chance of getting an A on each exam le

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Question 758796: suppose you will be taking exams in english, chemistry and statistics tomorrow. further, you know from past experience that you have a 50% chance of getting an A on each exam
let x be a random variable representing the number of A's you earn. show the probability distribution of X.
Answer by stanbon(75887) (Show Source):
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suppose you will be taking exams in english, chemistry and statistics tomorrow. further, you know from past experience that you have a 50% chance of getting an A on each exam
let x be a random variable representing the number of A's you earn. show the probability distribution of X.
P(x=0) = 0.5^3 = 0.125 = 1/8
P(x=1) = 3(0.5)^3 = 3/0.125 = 3/8
P(x=2) = 3(0.5)^3 = 3/0.135 = 3/8
P(x=3) = 0.5^3 = 0.125 = 1/8
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Expected # of A's = np = 3(1/2) = 1.5
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Or if you want to work it this way:
E(A) = 0*(1/8) + 1(3/8) + 2(3/8) + 3(1/8)
= [0+3+6+3]/8 = 12/8 = 1.5
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Cheers,
Stan H.