statistics

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?

1. 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

posted by Reiny
2. 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)

posted by gio
3. 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.)

posted by Glenda
4. 0999

posted by Anonymous

Similar Questions

1. Stat HW for.

1. A student taking a midterm exam in Ancient History comes to two questions pertaining to a lecture that he missed, and so he decides to take a random guess on both questions. One question is true-false and the other is multiple
2. Stats

An instructor gives a test with 20 multiple choice questions. There are 4 responses per questions and only one choice correct. The test also has 30 True/False questions. Determine the probability a student randomly guessing on all
3. 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
4. Statistical concept 68-95-99.7

1. A student taking a midterm exam in Ancient History comes to two questions pertaining to a lecture that he missed, and so he decides to take a random guess on both questions. One question is true-false and the other is multiple
5. math

You are writing multiple choice test. Each question has 5 choices, only one of which is correct. You have no idea how to answer three questions. What is the probability that you will get all three of these questions correct if you
6. elementary stats

On a multiple choice test with 11 questions, each question has four possible answers, one of which is correct. For students who guess at all answers, find the mean for the number of correct answers.
7. 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
8. Algebra

A test consist of 15 multiple choice questions, 12 true-false questions and 10 fill in the bland questions. you got 8 questions wrong. what percent of the answers were correct?
9. probability

a multiple choice test consists 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
10. statistics

A test consist of 10 multiple choice questions, each with five possible answers, one of which is correct. To past the test a student must get 60% or better
11. Statistics

There are 100 questions from a SAT test, and they are all multiple choice with possible answers of a,b,c,d,e for each question only one answer is correct. Find the mean number of correct answers for those who make random guesses

More Similar Questions