2. You take a 20-question multiple choice exam on which every correct answer is worth 1 point, and every incorrect answer is worth - points to discourage guessing. Each question has five options: (A) through (E). On each question, you are able to eliminate one of the options as certainly wrong (leaving four), and then guess randomly between the other four options. (a) The number of correct answers you give is a random variable X with a binomial distri- bution. What are the parameters (n and p) of that distribution? (b) Express the number of points you receive as a linear transformation aX+b of X, the random variable from part (a). (c) Find the probability that you get exactly 12.5 points.
2. You take a 20-question multiple choice exam on which every correct answer is worth 1 point, and every incorrect answer is worth - points to discourage guessing. Each question has five options: (A) through (E). On each question, you are able to eliminate one of the options as certainly wrong (leaving four), and then guess randomly between the other four options. (a) The number of correct answers you give is a random variable X with a binomial distri- bution. What are the parameters (n and p) of that distribution? (b) Express the number of points you receive as a linear transformation aX+b of X, the random variable from part (a). (c) Find the probability that you get exactly 12.5 points.
A First Course in Probability (10th Edition)
10th Edition
ISBN:9780134753119
Author:Sheldon Ross
Publisher:Sheldon Ross
Chapter1: Combinatorial Analysis
Section: Chapter Questions
Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...
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Transcribed Image Text:2. You take a 20-question multiple choice exam on which every correct answer is worth 1 point,
and every incorrect answer is worth - points to discourage guessing. Each question has five
options: (A) through (E). On each question, you are able to eliminate one of the options as
certainly wrong (leaving four), and then guess randomly between the other four options.
(a) The number of correct answers you give is a random variable X with a binomial distri-
bution. What are the parameters (n and p) of that distribution?
(b) Express the number of points you receive as a linear transformation aX+b of X, the
random variable from part (a).
(c) Find the probability that you get exactly 12.5 points.
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