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Pulsified333

  • one year ago

Transplant operations have become routine. One common transplant operation is for kidneys. The most dangerous aspect of the procedure is the possibility that the body may reject the new organ. There are several new drugs available for such circumstances and the earlier the drug is administered, the higher the probability of averting rejection. The New England Journal of Medicine recently reported the development of a new urine test to detect early warning signs that the body is rejecting a transplanted kidney. However, like most other tests, the new test is not perfect. In fact, 20% of negative tests and 6% of positive tests prove to be incorrect. Physicians know that in about 32% of kidney transplants the body tries to reject the organ. If the new test has a positive result (indicating early warning of rejection), what is the probability that the body is attempting to reject the kidney?

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  1. Pulsified333
    • one year ago
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    @satellite73 @dan815

  2. anonymous
    • one year ago
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    kind of wordy isn't it? probably a bayes formula question lets see if we can cut through the verbiage

  3. Pulsified333
    • one year ago
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    okay let me see

  4. anonymous
    • one year ago
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    this stuff is usually confusing as hell one way to break through the confusion is to forget about probability and percents, and work with nice large whole numbers to see what is going on

  5. anonymous
    • one year ago
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    lets say 10,000 people have the transplant how many try to reject the kidney?

  6. Pulsified333
    • one year ago
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    3200

  7. anonymous
    • one year ago
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    and how many don't ?

  8. Pulsified333
    • one year ago
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    6800

  9. anonymous
    • one year ago
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    20% of negative tests prove to be incorrect. how many is that?

  10. Pulsified333
    • one year ago
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    of 10000?

  11. anonymous
    • one year ago
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    no

  12. anonymous
    • one year ago
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    20% of negative tests are incorrect that means out of the 3200 people who DO reject, the test is negative and wrong

  13. Pulsified333
    • one year ago
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    oh

  14. Pulsified333
    • one year ago
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    so thats not the answer?

  15. anonymous
    • one year ago
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    what is 20% of 3200?

  16. Pulsified333
    • one year ago
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    640

  17. Pulsified333
    • one year ago
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    3200-640= 2560?

  18. anonymous
    • one year ago
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    those are the people who have a negative nest that is right

  19. anonymous
    • one year ago
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    now for the next part

  20. Pulsified333
    • one year ago
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    so is what I did wrong?

  21. anonymous
    • one year ago
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    wait i think i might have done something wrong, the posiive negative business is confusing lets back up a sec

  22. anonymous
    • one year ago
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    6800 do not reject 3200 do reject

  23. anonymous
    • one year ago
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    out of the the 3200 who do reject, 640 get the wrong answer (negative) and 2560 get the right answer

  24. Pulsified333
    • one year ago
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    so I have the answer in the work I did earlier

  25. anonymous
    • one year ago
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    no not yet, and i still got myself confused, damn we need to work the the 6% now

  26. anonymous
    • one year ago
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    ok we are good of the 6800 who do not reject 6% get the wrong answer (positive) so 408 get a positive

  27. anonymous
    • one year ago
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    now we can finish (thank god)

  28. anonymous
    • one year ago
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    If the new test has a positive result (indicating early warning of rejection), what is the probability that the body is attempting to reject the kidney? it is the number of people who do reject and test positive, divided by all that test positive

  29. anonymous
    • one year ago
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    the number that test positive (if i did it correctly) is 2560+408

  30. Pulsified333
    • one year ago
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    3608

  31. anonymous
    • one year ago
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    and the number of people who test positive and have it is 2560

  32. Pulsified333
    • one year ago
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    okay

  33. anonymous
    • one year ago
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    now we can try this using bayes formula and not numbers if you like just working with the percents as decimals

  34. Pulsified333
    • one year ago
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    Pr(A|B) = (Pr(B|A)Pr(A))/Pr(B)

  35. anonymous
    • one year ago
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    we need the percent of people that you test positive and have it, which is \[.32\times .80\]

  36. anonymous
    • one year ago
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    that is your numerator

  37. anonymous
    • one year ago
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    and you need percent who test positive \[.32\times .80+.68\times .06\]

  38. anonymous
    • one year ago
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    should be the same answer

  39. Pulsified333
    • one year ago
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    as?

  40. anonymous
    • one year ago
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    http://www.wolframalpha.com/input/?i=2560%2F%282560%2B408%29

  41. Pulsified333
    • one year ago
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    Which one?

  42. anonymous
    • one year ago
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    i made a typo in the first one http://www.wolframalpha.com/input/?i=%28.32*.80%29%2F%28.32*.80%2B.06*.68%29

  43. anonymous
    • one year ago
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    they are the same

  44. Pulsified333
    • one year ago
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    I see

  45. Pulsified333
    • one year ago
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    :D it worked thanks.

  46. Pulsified333
    • one year ago
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    I have to finish as fast as I can so that I can study for my midterm tomorrow

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