Question

Each question on a multiple-choice exam has four choices. One of the choices is correct, worth four points. Another choice is wrong but carries partial credit of one point. The other two choices are wrong and worth negative one point. If a student picks answers at random, what is the expected value of his or her score for a problem?
A 0.75
B 0.25
C 1.25
D 1.50

Answer 1

Answer:A)0.75

Step-by-step explanation:

Given

There are four options to a question

out of which one is correct with 4 points

one is wrong but carries 1 point

Other two are wrong with a negative Point

Probability of selecting an option is $\frac{1}{4}$

Expected score$=\frac{1}{4}\times 4+\frac{1}{4}\times 1+\frac{1}{4}\times (-1)+\frac{1}{4}\times (-1)$

Expected score=1+0.25-0.5

Expected score=0.75