Results 1 to 2 of 2

Math Help - Conditional probability question

  1. #1
    Junior Member
    Joined
    Feb 2009
    Posts
    57

    Conditional probability question

    A blood test is 90% effective in detecting a disease. It also falsely diagnoses that a healthy person has the disease 3% of the time. If 10% of those tested have the disease, what is the prob. that a person who tests positive will actually have the disease?

    Is this right?
    P(Has Disease | Positive test) = 0.90 * 0.1 / 0.90 * 0.1 + 0.03 * 0.1 = 0.96
    Last edited by vexiked; November 16th 2009 at 02:27 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by vexiked View Post
    A blood test is 90% effective in detecting a disease. It also falsely diagnoses that a healthy person has the disease 3% of the time. If 10% of those tested have the disease, what is the prob. that a person who tests positive will actually have the disease?

    Is this right?
    P(Has Disease | Positive test) = 0.90 * 0.1 / 0.90 * 0.1 + 0.03 * 0.1 = 0.96
    I calculate P(Has Disease | Positive test) = (0.90 * 0.1)/(0.90 * 0.1 + 0.03 * 0.9).
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: July 22nd 2011, 02:39 AM
  2. Conditional Probability Question
    Posted in the Advanced Statistics Forum
    Replies: 4
    Last Post: February 7th 2010, 08:12 AM
  3. Conditional Probability question
    Posted in the Statistics Forum
    Replies: 1
    Last Post: January 22nd 2010, 08:47 AM
  4. Conditional Probability Question
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: October 5th 2009, 10:16 AM
  5. Conditional probability question
    Posted in the Statistics Forum
    Replies: 1
    Last Post: September 3rd 2009, 04:00 PM

Search Tags


/mathhelpforum @mathhelpforum