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Math Help - Binomial Distribution Questions (success/failure)

  1. #1
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    Binomial Distribution Questions (success/failure)

    Suppose that 65% of the families in a town own computers. If eight families are surveyed at random,

    a.) what is the probability that at least four own computers?

    b.) waht is the expected number of families with computers?
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  2. #2
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    These are definition problems, not calculation problems. There is some calculating involved...

    a) Pr(At Least 4) = Pr(4) + Pr(5) + Pr(6) + Pr(7) + Pr(8). Can you write the individual probabiltiies? You should be able to.

    b) The mean of the distribution is...? n*p should ring a bell.
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  3. #3
    Senior Member JaneBennet's Avatar
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    For (a), P(at least 4) = 1 − P(less than 4) = 1 − [P(1) + P(2) + P(3)]. Now you have three probabilities rather than five to calculate.
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  4. #4
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    Frankly, to gain familiarity, I'd suggest calculating and writing the entire distribution. A slightly easier way is nice, but it's harder to program that kind of decision making and you may learn less along the way.

    My views. I welcome others'.

    TKHunny - Brute Force Meister
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