130k views
5 votes
If she completely guesses on all of the questions, what is the probability that she gets two of the four questions correct?

If she completely guesses on all of the questions, what is the probability that she-example-1

1 Answer

5 votes

Answer:

D) 0.211

Explanation:

The probability of getting a correct answer is 1/4, so the probability of an incorrect answer is 3/4.

The probability of 2 correct and 2 incorrect is (1/4)(1/4)(3/4)(3/4) = 9/256.

There are C(4,2) = 4·3/(2·1) = 6 ways to have some combination of 2 correct and 2 incorrect out of 4 questions. So, the probability of that result is ...

... 6 · 9/256 = 27/128 =0.2109375 ≈ 0.211

User Andrei Chevozerov
by
9.2k points