Question

Andy Dwyer takes an exam for his women's studies class at Pawnee Community College. The exam has 20 multiple choice questions, each with 5 answer choices. If he simply guesses on each question, which of the following represents the probability that he gets 3 or fewer questions correct?

Select one:

None of these, this does not fit a binomial model.

b(20,0.8,0) + b(20,0.8,1) + b(20,0.8,2) + b(20,0.8,3)

b(20,0.2,0) + b(20,0.2,1) + b(20,0.2,2)

b(20,0.2,0) + b(20,0.2,1) + b(20,0.2,2) + b(20,0.2,3)

b(20,0.8,0) + b(20,0.8,1) + b(20,0.8,2)

Answer 1

To find out the theoretical probability of the case given, we need to make certain assumptions.

First, we'll assume that he'll attempt all of the questions, i.e he'll attempt all 20 questions.

Next assumption is that each option in each question is equally likely to be marked by the student.

This pretty much leads us to a binomial probability distribution.

where b(n, p, k) is a binomial model with

n=20, p=0.2 and

k=0,1,2,3