Results 1 to 2 of 2

Math Help - Multiple choise test probability!? Help!!

  1. #1
    Newbie
    Joined
    Apr 2009
    Posts
    2

    Multiple choise test probability!? Help!!

    teacher give a 20 question multiple choice test. There are 4 possible answers and only one is correct. Find the probability that the student..

    a) Gets exactly 19 right
    b)Gets at least 1 right

    I'm guessing this has to do with binomial probability.. since there is 4^20 answers.

    not sure how you would set this up. Any help is appreciated!

    Okay, so for A) it would be 20C19 x (.25)^19x(.75)^1 ????? I got 5.46%?????


    And for B)

    1- minus part A , which is 99%

    Right????
    Last edited by mr fantastic; May 3rd 2009 at 09:27 PM. Reason: Restored original questions
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Nov 2008
    Posts
    461
    Hello.

    Quote Originally Posted by stephy7878 View Post
    teacher give a 20 question multiple choice test. There are 4 possible answers and only one is correct. Find the probability that the student..

    a) Gets exactly 19 right
    b)Gets at least 1 right

    I'm guessing this has to do with binomial probability.. since there is 4^20 answers.

    not sure how you would set this up. Any help is appreciated!

    Okay, so for A) it would be 20C19 x (.25)^19x(.75)^1 ?????
    Yup
    Quote Originally Posted by stephy7878 View Post
    I got 5.46%?????
    No; 20C19 = 20, 0.25^(19) is nearly 0

    Quote Originally Posted by stephy7878 View Post
    And for B)

    1- minus part A , which is 99%

    Right????

    Minus Part A? what? I thought your solution for A was 5.46%?

    Anyway; you need to find

    1 - prob("all 20 answers are incorrect") = 1 - prob("0 answers are correct")

    where prob("20 anwers are incorrect") = 20C0 *0.25^0*0.75^20 = 0.003 = 0.3%
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Hypothesis test for multiple categorical groups
    Posted in the Statistics Forum
    Replies: 5
    Last Post: July 12th 2011, 05:56 AM
  2. Question about F-Test for comparing multiple regression models
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: March 10th 2011, 07:38 PM
  3. Replies: 0
    Last Post: July 30th 2010, 01:21 AM
  4. Replies: 2
    Last Post: May 21st 2010, 10:56 AM
  5. Multiple linear regression: partial F-test
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: June 23rd 2009, 12:54 AM

Search Tags


/mathhelpforum @mathhelpforum