A multiple-choice test consists of ten questions, each with A-E answers. If you guess the answer to each question, how many questions can you expect to get correct? Also find the standard deviation of the number of questions you can expect to get correct.
A) 1, 1.6
B) 3, 1.3
C) 2, 1.3
D) 1.2, 1.6

Question

Quizplus · Accepted Answer

The expected value for guessing a single question with five options is 1/5. For ten questions, the expected value would be 10/5 = 2. The standard deviation for the number of correct answers when guessing is √(npq) where n is the number of trials (10), p is the probability of success (1/5) and q is the probability of failure (4/5). Calculating this gives a standard deviation of approximately 1.3. Therefore, the correct choice is C.

A Multiple-Choice Test Consists of Ten Questions, Each with A-E