Results 1 to 6 of 6

Math Help - Multiple choice problems - stats

  1. #1
    Junior Member
    Joined
    Mar 2008
    Posts
    41

    Multiple choice problems - stats

    1. If P(A) =.2 and P(B)=.1 , what is P(A U B) if A and B are independent?

    a) .02
    b) .28
    c) .30
    d) .32







    2. Given that 52% of the u.s. population are female and 15% of the U.S. population are older than age 65, can we conclude that (.52)(.15)=7.8% are women older than age 65?

    a) Yes, by the multiplication rule.
    b) Yes, by conditional probabilities.
    c) Yes, by the Law of Large Number
    d) No, because the events may not be independent
    e) No, because the events may not be disjoint





    3.Given that the probabilities P(A)=.4 and P(A U B)=.6, what is the probability P(B) if A and B are mutually exclusive (disjoint)?

    a) 1
    b) .6
    c) .24
    d) .2
    e) cannot be determined

    4. Which of the following pairs of events are disjoint?

    a) A: the odd numbers; B: the number 5
    b) A: the even numbers; B: the numbers greater than 10
    c) A: the numbers less than 5; B: all negative numbers
    d) A: the numbers above 100; B: the numbers less than -200
    e) A: negative numbers; B: odd numbers

    5. Suppose X is a random variable with a mean of m. Suppose we observe X many times and keep track of the average of the observed values. The law of large numbers says that....

    a) the value of m will get larger and larger as we keep observing X.
    b) this average and the value of m will both continue to get larger.
    c) this average will get closer to m as we keep observing X.
    d) this average will become 0.
    e) this average will decrease as we keep observing X.


    6. In a population of students, the number of calculators owned is a random variable X with P(X=0)=.2 , P(X=1)=.6, and P(X=2)=.2 .The mean of this probability distribution is..

    a) 0
    b) 2
    c) 1
    d) .5
    e) unable to be determined

    7. Refer to the information in problem #6 above. The variance of this probability distribution is..

    a) 1
    b) .63
    c) .5
    d) .4
    e)unable to be determined

    8) Given that 1% of batteries are ineffective, what is the probability that all 4 batteries in a package are effective.

    a) .000001%
    b) 1%
    c) 96.06%
    d) 99%
    e) 99.999999%

    9. The number of calories in a one-ounce serving of fruit loops is a random variable with a mean of 110. The number of calories in a cup of milk is a random variable with a mean of 140. For breakfast, you eat one ounce of cereal with 1/2 cups of milk. Let Z be the random variable that represents the total number of calories in this breakfast. The mean of Z is...

    a) 110
    b) 125
    c) 140
    d) 180
    e) 250

    10) The weight of a bag of candy is normally distributed with a mean of 60g and standard deviation of 2g. What is the probability that the next bag will weigh less than 55g?

    a) .62%
    b) 3.3%
    c) 3.6%
    d) 50%
    e) 99.38%




    MY ANSWERS
    -------------
    1. C
    2. D
    3. D
    4. ?
    5. C
    6. C
    7. ?
    8. C
    9. E
    10. B
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Apr 2008
    Posts
    33
    Changed 10 from b to A. Simple normal cdf(0,55,60,2)
    Last edited by Bradley55; January 11th 2009 at 04:25 PM.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Bradley55 View Post
    Changed 10 from b to A. Simple normal cdf(0,55,60,2)
    Since it's a normal model the lower value is actually -oo.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Airjunkie View Post
    [snip]
    4. Which of the following pairs of events are disjoint?

    a) A: the odd numbers; B: the number 5
    b) A: the even numbers; B: the numbers greater than 10
    c) A: the numbers less than 5; B: all negative numbers
    d) A: the numbers above 100; B: the numbers less than -200
    e) A: negative numbers; B: odd numbers

    [snip]

    6. In a population of students, the number of calculators owned is a random variable X with P(X=0)=.2 , P(X=1)=.6, and P(X=2)=.2 .The mean of this probability distribution is..

    a) 0
    b) 2
    c) 1
    d) .5
    e) unable to be determined


    7. Refer to the information in problem #6 above. The variance of this probability distribution is..

    a) 1
    b) .63
    c) .5
    d) .4
    e)unable to be determined

    [snip]
    MY ANSWERS
    -------------
    1. C
    2. D
    3. D
    4. ?
    5. C
    6. C
    7. ?
    8. C
    9. E
    10. B
    I will help with the two you flagged with ? (Furthermore, Q6 is correct and I agree with the previous poster regarding Q10).

    4. Apply the definition: Two sets are disjoint if they have no elements in common (that is, their intersection is the null set).

    7. Apply the definition: Var(X) = E(X^2) - \overline{X}^2 = E(X^2) - 1^2 and E(X^2) is readily calculated from the given data.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Mar 2008
    Posts
    41
    MY *new*ANSWERS
    -------------
    1. C
    2. D
    3. D
    4. D new
    5. C
    6. C
    7. ?
    8. C
    9. E
    10. A new


    Still cant grasp #7
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by Airjunkie View Post
    MY *new*ANSWERS
    -------------
    1. C
    2. D
    3. D
    4. D new
    5. C
    6. C
    7. ?
    8. C
    9. E
    10. A new


    Still cant grasp #7
    Where are you stuck in calculating E(X^2)?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. trigonometry : multiple choice problems
    Posted in the Trigonometry Forum
    Replies: 3
    Last Post: June 13th 2011, 04:47 AM
  2. Stats help - multiple choice part 1
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: May 3rd 2009, 01:34 PM
  3. Stats help - multiple choice part 2
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: May 3rd 2009, 01:34 PM
  4. RE: Multiple choice problems
    Posted in the Business Math Forum
    Replies: 1
    Last Post: March 4th 2008, 03:56 AM
  5. Calculus Problems Multiple Choice
    Posted in the Calculus Forum
    Replies: 3
    Last Post: April 20th 2006, 01:54 AM

Search Tags


/mathhelpforum @mathhelpforum