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Math Help - Probability

  1. #1
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    Probability

    Ok.. again I landed a professor who never attends class and goes away to give conference. I'm stuck on this, help please? Thank you.

    Is this right?

    (9) Probability of getting an infection is .01, probability of test being positive given I have the infection is 0.9, and the probability of the test being positive given I do not have the infection is 0.4. I tested positive, what is the new probability that I have a staph infection?

    [(0.9)(.01)] / [(09)(.01)] + [(.4)(.99)] = .022

    ---------------------------------------------------------------

    And here I am lost

    (5)Suppose you invest $1000 in Euros. If the Euro appreciates relative to the dollar it will be worth $1200 in one year. However if the euro devalues your money will be worth $900 in one year. The probability of the US playing hardball with Europe is 0.3.

    (a) Compute the expected value you will have in one year,

    (b) Suppose you do this investment one time
    1. What is the most you will gain?
    2. What is the most you will lose?
    3. Can you gain or lose any other amount than the previous answers?

    (c) Suppose we repeat this investment 100 times:
    1. What is the most you will gain?
    2. What is the most you will lose?
    3. How much can you expect to win/lose?

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    (13)
    E be the event {KH, KD, KC, JD}
    F be the event {KH, KS, QH}
    G '' '' '' {KH, KD, QH, QC}

    Are the events E and F independent?

    Are the events E and G independent?

    Are the events E and F independent given event G?

    ------------------------------------------------------------------

    (4)
    Here I got the first two parts but then...

    "H" is dominant for huntington's disease. Sam does not have the disease (is hh). Mary is too young to tell if she has inherited the disease, however both of her parents have it, and each parent has a parent who does not have it.

    If Sam has a child with Mary, what is the probability of the child having Huntington's disease?

    I see that

    Mary's dad (Hh) Mom (Hh) so Mary has 75% chance of not having it.

    Mary's grandpa 1= (Hh) Grandma 1= (hh) Grandpa 2= (Hh) Grandma 2=(hh)

    but how to include all of it to compute for an answer?

    Thanks again
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  2. #2
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    Quote Originally Posted by domain07 View Post
    Ok.. again I landed a professor who never attends class and goes away to give conference. I'm stuck on this, help please? Thank you.

    Is this right?

    (9) Probability of getting an infection is .01, probability of test being positive given I have the infection is 0.9, and the probability of the test being positive given I do not have the infection is 0.4. I tested positive, what is the new probability that I have a staph infection?

    [(0.9)(.01)] / [(0.9)(.01)] + [(.4)(.99)] = .022
    [snip]
    Looks OK (I haven't checked the arithmetic).
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