A test consists of 5 questions.
A correct answer scores 2 marks and an incorrect one scores -1.
Assuming that all the questions are answered, find probability of scoring -2.
I figured that only way to score -2 is 1 correct and 4 incorrect: (1)(2) + 4(-1) = -2
. . Right!
Can you guys give me a hint on how to proceed further?
I assume that the student is randomly guessing the answers,
. . and that the probability of guessing a correct answer is
To get a score of -2, he must get one Correct and four Incorrect, in some order.
There are 5 choices for the Correct answer.
The probability that answer being correct is
He must get the other four equations Incorrect.
The probability of this is: