10. A test consisting of 25 multiple-choice questions with 5 answer choices for each question is administered For each question; there is only | correct answer Let X be the number of correct answers if a student guesses randomly from the 5 choices for each of the 25 questions What is the probability distribution of X? This test, like many multiple-choice tests, is scored using penalty for guessing: The test score is determined by awarding point for each question answered correctly, deducting 0.25 point for each question answered incorrectly, and ignoring any question that is omitted. That is, the test score is calculated using the following formula Score = number of correct answers) (0.25 number of incorrect answers) + (0 number of omits) For example, the score for a student who answers 17 questions correctly, answers 3 questions incorrectly, and omits 5 questions is Score 17) - (0.25 * 3) + (0 x 5) = 16.25 Suppose student knows the correct answers for 18 questions, answers those 18 questions correctly, and chooses randomly from the 5 choices for each of the other 7 questions. Show that the expected value of the student'$ score is 18 when using the scoring formula above



Answer :

Using the given formula, we have been able to prove that; the expected value of the students' score is 18 correct responses

How to solve binomial probability distribution problems?

1) Let X denote the number of correct guesses, assuming that a student guesses randomly among the five options of all 25 questions. Then X has a binomial probability distribution with;

n = 25

p = 1/5 = 0.2

2) Let Y denote the number of correct responses on the seven questions for which the student guesses randomly from among the five options. Then Y has a binomial probability distribution with n = 7 and p = 0.20. Then the expected value of Y is;

E(Y) = np = 7(0.2) = 1.4

Using the scoring formula given, we have;

Score = (18 + Y) - 0.25(7 - Y) + 0(0)

= 16.25 + 12Y

The expected value of the students' score is;

E(16.25 + 12Y) = 16.25 + 12(1.4)

= 18 correct responses.

Read more about Binomial probability distribution at; https://brainly.com/question/15278907

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