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Old 07-25-2007   #1
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Default Probability of Blood Types?

The probability that a person in The United States has type O+ blood is 38%. Three unrelated people are selected at random in the United Statesa) find the probability that all three have type o+ bloodb) find the probability that none of the three has type o+ bloodc) find the probability that at least one of the three has type o+ blood
Old 07-25-2007   #2
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a) Each event is independent, so multiply the chances of an event occurring three times.0.38 ^ 3 = 0.055b) The chance of the subject NOT having O+ blood is 1 - 0.38, 0.62. After figuring that out, just repeat the process from part a).0.62 ^ 3 = 0.24c) The chance of there being at least one person with O+ blood is 1 - P where P is the chance of all three not having O+. That means it is just 1 - b), or 0.76.Two quick comments: one is I am rounding off to two sig figs because clearly 0.38 is only precise to two significant figures anyway. The other is, who is giving thumbs down to right answers? The fourth answer is correct and didn't deserve a thumbs down, now did it?
Old 07-25-2007   #3
Bryan W
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a) .38 X .38 X.38B) (1-.38) X (1-.38) X (1-.38)c) im not as positive
Old 07-25-2007   #4
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a) 0.38x0.38x0.38=0.054872b) 0.62x0.62x0.62=0.238328c) (0.38x0.62x0.62x3)+(0.38x0.38x0.62x3)+(0.38x0.38x0 .38)= 0.438216+0.268584+0.054872= 0.761672

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