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Thread: Probability!

  1. #1
    Junior Member
    Apr 2006


    Need some help on this one, i get confused with the second one especially. i have the first and the 3rd one worked out!

    The table below describes the smoking habits of a group of asthma sufferers.

    Light Heavy
    Non-Smoker Smoker Smoker Total__
    Men 432 35 31 498
    Women 438 39 43 520
    Total 870 74 74 1018

    a. If a person is randomly selected, find the probability that he or she is not a light smoker.
    b. If a person is randomly selected, find the probability of getting a woman given that she is a nonsmoker.
    c. Assuming we were to consider a random sample of 13,000 people, how many would you predict are men who are heavy smokers based on the results given here?
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  2. #2
    Mar 2008
    Think about probability as (size of group satisfying the condition) divided by ( total size of group).

    So for the first problem it is:
    (total number of non-light smokers) / (total number of people).

    The second problem is conditional probability: Imagine I select a person at random and don't show you who they are. All I tell you is that the person selected is a nonsmoker. Now tell me how likely it is that they are a woman?

    For the last problem assume that the sample group represents the actual population's proportions of smokers to non-smokers, heavy to light, etc. So what percentage of the total sample are male heavy smokers? What number of people is this percentage of 13,000?
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