Results 1 to 11 of 11

Math Help - another probability problem!

  1. #1
    Newbie
    Joined
    Aug 2011
    Posts
    7

    another probability problem!

    From the past studies it is know that 60% of the students at HIGH read the Age newspaper. There was a recent article in the Age on the rise in living costs in Melbourne. If the class size is 20,

    A) what is the probability that none of the students read the article?
    B) what is the probability that at least 75% of the students read the article?

    Do I use the bionomial probability?

    I am hopeless at math. Any hints or input would be muchly appreciated.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Siron's Avatar
    Joined
    Jul 2011
    From
    Norway
    Posts
    1,250
    Thanks
    20

    Re: another probability problem!

    Yes, the binomial contribution is fine.
    Can you now solve the problem? ...
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Aug 2011
    Posts
    7

    Re: another probability problem!

    Its nice to know i am on the right track!
    i was taught calculating binomial using the nCr calculator function today. Im just still unsure of what the terms p and n is...
    the 60% really throws me off and gets me confused...
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor Siron's Avatar
    Joined
    Jul 2011
    From
    Norway
    Posts
    1,250
    Thanks
    20

    Re: another probability problem!

    The best way to recognize if you're dealing with a binomial distribution (it has to be distribution not contribution, sorry for that) is to see if you've success or not, in this case you've success if they read the article and no success if they don't so it's a binomial distribution.

    Use: p=0,6 and n=20
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Aug 2011
    Posts
    7

    Re: another probability problem!

    ill be sure to keep that in mind.

    = 1.0995 ?

    fingers crossed its correct.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor Siron's Avatar
    Joined
    Jul 2011
    From
    Norway
    Posts
    1,250
    Thanks
    20

    Re: another probability problem!

    Is this the answer to question a)?
    Can you show me how you've calculated it, because honestly I've no calculator over here .
    For question b) Have you any idea how to solve that one?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Aug 2011
    Posts
    7

    Re: another probability problem!

    P(X=0): 20C0 * 0.6^0 * 0.4^20-0 = 1.0995

    and still no clue for question b)
    >.<
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor Siron's Avatar
    Joined
    Jul 2011
    From
    Norway
    Posts
    1,250
    Thanks
    20

    Re: another probability problem!

    a) Check your calculation again, a probability P can never be >100%.
    b) What's 75% of 20? Important here is the 'at least' that means 75% or more so ...
    Last edited by Siron; August 18th 2011 at 09:38 AM.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    MHF Contributor

    Joined
    Apr 2005
    Posts
    14,973
    Thanks
    1121

    Re: another probability problem!

    Quote Originally Posted by iamamathnoob View Post
    P(X=0): 20C0 * 0.6^0 * 0.4^20-0 = 1.0995
    No. 20C0= 1 (nC0= 1 for all n), 0.6^0= 1 (any number to the 0 power is 1) and 0.4^20 is a very small number.

    and still no clue for question b)
    >.<
    "At least 75%" means "at least 15". You will need to calculate the probability for 15, 16, 17, 18, 19, and 20, and add.
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Newbie
    Joined
    Aug 2011
    Posts
    7

    Re: another probability problem!

    yeah that's the idea i had for question b) to calculate the probability for 15, 16, 17, 18, 19, and 20, and add...

    thanks guys, you have been a very big help =)
    Follow Math Help Forum on Facebook and Google+

  11. #11
    MHF Contributor Siron's Avatar
    Joined
    Jul 2011
    From
    Norway
    Posts
    1,250
    Thanks
    20

    Re: another probability problem!

    You're welcome! And indeed these 'little words' like: at least, at most, ... are really important to understand the problem.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Probability Problem...
    Posted in the Advanced Statistics Forum
    Replies: 7
    Last Post: October 22nd 2011, 06:57 AM
  2. Replies: 10
    Last Post: January 21st 2011, 11:47 AM
  3. Replies: 0
    Last Post: October 8th 2009, 08:45 AM
  4. Probability Problem
    Posted in the Statistics Forum
    Replies: 1
    Last Post: October 1st 2009, 07:51 AM
  5. probability problem
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: January 2nd 2008, 04:38 PM

/mathhelpforum @mathhelpforum