Results 1 to 5 of 5

Math Help - Probability of independent studies question

  1. #1
    Member
    Joined
    Jun 2006
    Posts
    165

    Probability of independent studies question

    The probability that Andy studies math over break is 0.3 and the probability that Betty independently studies over break is 0.4. Find the probability Andy studies math over break and Betty doesn't.

    P(B)=0.4 P(B)=1-0.4=0.6
    P(A)=0.3 P(A)=1-0.3=0.7, Ok this is where I'm stuck do I add, Multi, or divide. List of possible answer are. My answer is 0.42 by going from my text book. Is this right. Thanks for any help given.

    1. 0.12
    2. 0.42
    3. 0.18
    4. 0.46
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by kwtolley
    The probability that Andy studies math over break is 0.3 and the probability that Betty independently studies over break is 0.4. Find the probability Andy studies math over break and Betty doesn't.

    P(B)=0.4 P(B)=1-0.4=0.6
    P(A)=0.3 P(A)=1-0.3=0.7, Ok this is where I'm stuck do I add, Multi, or divide. List of possible answer are. My answer is 0.42 by going from my text book. Is this right. Thanks for any help given.

    1. 0.12
    2. 0.42
    3. 0.18
    4. 0.46
    Yes these are independent events so their probabilities multiply.

    That it cannot be the sum can be shown by supposing both events have
    probability 0.7, clearly the probability of both occurring is <1, so it cannot be
    the sum.

    RonL
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor Quick's Avatar
    Joined
    May 2006
    From
    New England
    Posts
    1,024
    I'm just going to show the work (you can figure out why it works):

    P(A\not{B})=P(A)\times(1-P(B))

    substitute: P(A\not{B})=0.3\times(1-0.4)

    subtract: P(A\not{B})=0.3\times0.6

    multiply: P(A\not{B})=0.18= 18\%
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Jun 2006
    Posts
    165

    Smile thank you both

    thanks quick for showing me the brake down.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by kwtolley
    thanks quick for showing me the brake down.
    I for one am much happier answering you questions now that you are
    indicating some of your thinking.

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Economics Homework Help - Replacement Studies
    Posted in the Business Math Forum
    Replies: 1
    Last Post: July 23rd 2011, 11:07 PM
  2. Case-control studies
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: April 30th 2010, 01:28 AM
  3. Independent probability?
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: July 9th 2008, 10:45 PM
  4. Independent Pre Algebra Studies Help
    Posted in the Algebra Forum
    Replies: 0
    Last Post: May 1st 2008, 06:18 AM
  5. Independent probability
    Posted in the Statistics Forum
    Replies: 4
    Last Post: August 8th 2006, 09:45 PM

Search Tags


/mathhelpforum @mathhelpforum