In answering a question on a multiple-choice test, a student either knows the answer or guesses. Let p be the probability that the student knows the answer and 1-p be the probability that the student guesses. Suppose there are 5 multiple-choice alternatives so a student who guesses at the answer will be correct with probability 1/5. (a) Show that the probability that a student knew the answer to a question given that he or she answered it correctly is 5p/(1+ 4p). (b) What is the probability that a student actually guessed the answer to a question given that he or she answered it correctly?

A First Course in Probability (10th Edition)
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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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In answering a question on a multiple-choice test, a student either knows the answer or guesses.
Let p be the probability that the student knows the answer and 1-p be the probability that the
student guesses. Suppose there are 5 multiple-choice alternatives so a student who guesses at the
answer will be correct with probability 1/5.
(a) Show that the probability that a student knew the answer to a question given that he or she
answered it correctly is 5p/(1+4p).
(b) What is the probability that a student actually guessed the answer to a question given that he
or she answered it correctly?
Transcribed Image Text:In answering a question on a multiple-choice test, a student either knows the answer or guesses. Let p be the probability that the student knows the answer and 1-p be the probability that the student guesses. Suppose there are 5 multiple-choice alternatives so a student who guesses at the answer will be correct with probability 1/5. (a) Show that the probability that a student knew the answer to a question given that he or she answered it correctly is 5p/(1+4p). (b) What is the probability that a student actually guessed the answer to a question given that he or she answered it correctly?
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