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 gets two of the four questions correct class=](https://us-static.z-dn.net/files/d21/c592a6a90b98e19689ddf1db0f65aa9d.png)
Answer:
D) 0.211
Step-by-step 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