statistics

posted by .

A multiple choice test has 20 questions with each having 4 possible answers with one correct. Assume a student randomly guesses the answer to every question.

1) What is the probability of getting exactly 9 correct answers?

2)What is the probability of getting less than 9 correct answers?

  • statistics -

    prob of R(ight) = 4/20 = 1/5
    prob of W(rong) = 4/5

    1) to have exactly 9R and 11W
    = C(20,9)((1/5)^9(4/5)^11
    = ....

    ( I got .00722)

    2) to get the prob of less than 9 you will have to do
    prob(0R) + prob(1R) + prob(2R) + .. + prob(8R)

    I will do prob(R4)
    = C(20,4)(1/4)^4(4/5)^16 = .21819

    Follow the same pattern for the other calculations

  • statistics -

    a test consists of 25 multiple choice questions. Each has 5 possible answers, which only one is correct. If a student guesses on each question, find the following:
    a) prob that he will guess all of them right
    b)prob that he will guess at most 12 right
    c) prob that he will guess at least 1 right
    d) mean and stndrd. deviation of the number of correct answers
    e)estimate the prob of the number of correct answers that will fall within the limits -----> miu +or- 2(stand.dev)

  • statistics -

    Suppose a student takes a 20 question multiple-choice test and guesses at every answer. If there are exactly four choices on each question, what is the probability the student passes the test? (Assume passing means the student gets at least 60% of the questions correct.)

  • statistics -

    0999

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Math

    10 multiple choice questions each with three possible answers only one of which is correct. A student guesses the answer to every question. (a)What is the probability that the student will answer the first six questions correctly and …
  2. Statistics

    A multiple choice test consists of 60 questions. Each question has 4 possible answers of which one is correct. If all answers are random guesses, estimate the probability of getting at least 20% correct?
  3. statistics

    10. A student is taking a multiple choice test where each question have 5 possible answers of which only one is right. If the student knows the answer the student answers correctly, otherwise there is a 20% probability of correct answer. …
  4. statistics

    A student is taking a multiple choice test where each question have 5 possible answers of which only one is right. If the student knows the answer the student answers correctly, otherwise there is a 20% probability of correct answer. …
  5. advanced statistics

    suppose a student takes a multiple choice test with 10 questions. suppose each question has 4 possible answers. if the student guesses randomly on each questions,what is the probability that the student gets exactly 6 correct?
  6. probability and statistics

    a multiple choice test onsists of 8 questions, each with 4 possible answers but only one of which is correct.what is the probability that an unprepared student will, by chance, get, a. all correct answers, b. exactly 5 correct answers, …
  7. statistics

    A math test consists of 17 multiple choice questions, each with five possible answers (a, b, c, d, e), only one of which is correct. Assume that a student takes the test and randomly answers the questions. What is the probability that …
  8. Statistics

    An unprepared student is about to take his first test of the semester. He is told that his test will be composed of 20 multiple choice questions, each with 4 possible answers, only one of which is correct. a.What is the probability …
  9. Statistics Algebra 2

    A 10-question multiple choice test has 4 possible answers for each question. A student guesses on all ten answer. a)What is the probability that the student selects at least 6 correct answers?
  10. statistics

    Suppose a multiple choice test has 20 questions with each question having 4 choices, only one of which is correct that is %25. suppose an unprepared student writes the answers, each time randomly picking on the 4 choices. what is the …

More Similar Questions