A multiple-choice test has 25 questions, each with 4 options. A student guesses randomly.
What are mean and SD of correct answers?
- Acheck_circle
mean 6.25, SD ≈ 2.165
- B
mean 12.5, SD 2.5
- C
mean 25, SD 4
- D
mean 6.25, SD 4.69
Explanation
p = 0.25. Mean = 25(0.25) = 6.25. SD = sqrt(25<em>0.25</em>0.75) = sqrt(4.6875) ≈ 2.165.