Results 1 to 5 of 5

Math Help - [SOLVED] probability sampling

  1. #1
    Newbie
    Joined
    Oct 2008
    Posts
    16

    Exclamation [SOLVED] probability sampling

    When I open a bank account i am allocated a 4 digit personal identification number(which may begin with one or more zeros) at random with all possibilites equally likely. Find the probability that:

    The digits im my number are in strictly increaing order.

    Can some please help me with this probabilty problem.

    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1
    If we take any selection of four digits, ex. (4,9,4,8), we can always arrange the four is ascending order: (4,4,8,9). Thus, all we need to finish is to determine how many possible four-selections are there.
    { {4+10-1} \choose 4} and there are 10^4 possible pin numbers.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2008
    Posts
    16
    Quote Originally Posted by Plato View Post
    If we take any selection of four digits, ex. (4,9,4,8), we can always arrange the four is ascending order: (4,4,8,9). Thus, all we need to finish is to determine how many possible four-selections are there.
    { {4+10-1} \choose 4} and there are 10^4 possible pin numbers.
    I understand that there are 10^4 possible pin numbers but i do not understand what means.

    can you please clarify what you mean by this.

    I thought the the answers was:

    10! / (4!(10-4)!))/10 ^ 4

    which is equall to 210/10 ^ 4

    thanks
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1
    That is the selection formula: { {K+N-1} \choose K}, { {M} \choose J}=\frac {M!}{(M-J)!(J!)} .

    If we have N difference types of items from which we are to select K items, we may pick more than one of any type.
    For example you are to pick four pieces of fruit from apples, oranges, or bananas.
    You may pick two apples and two bananas.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Oct 2008
    Posts
    16
    Thanks once again for helpping me.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Probability Sampling with replacement
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: September 18th 2012, 11:39 AM
  2. Probability - sampling without replacement.
    Posted in the Statistics Forum
    Replies: 4
    Last Post: May 17th 2011, 12:46 PM
  3. Probability Sampling and Sampling Methods
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: March 16th 2011, 04:41 AM
  4. Probability Sampling Question
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: March 12th 2011, 12:27 PM
  5. probability and sampling distributions
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: August 27th 2008, 10:42 PM

Search Tags


/mathhelpforum @mathhelpforum