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Thread: Understanding independent events.

  1. #1
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    Understanding independent events.

    There is a problem I do not understand:

    Government data show that 8% of adults are full-time college students and that 30% of adults are age 55 or 0lder. Nonetheless, we can't conclude that because (.08)(.30) = .024 or about 2.4% of adults are college students or older. Why not?

    The book answer is that: Independence is not a reasonable assumption.

    Independence is where one event will affect the outcome of the other. I cannot think of where this would occur in this case. Seems to me that the events are independent.

    Can someone fix my thinking.

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    Re: Understanding independent events.

    If I told you that somebody was 19 years old you might guess at a probability that they are in college. If I told you that somebody was 79 years old you could also guess at the probability that they're in college. Are those two numbers the same in your mind? If age and "being a full time college student" are independent then those numbers would have to be the same. But most likely you place the probability for the 19 year old to be higher than the probability for the 79 year old.
    I don't have emotions and sometimes that makes me very sad.

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