A student takes a multiple choice question exam that has 10 questions. Each question has 5 choices. What is the probability that they get exactly 3 correct an

Question

This is a college statistical extra practice question. I have no idea how to compete it. 

Answer 1

You need to decide what distribution to use.  There are a fixed number of questions (10).  The probability is the same for each question (1/5=0.2).

 

This is a binomial situation.

 

They are only asking about 1 point (3 correct responses) . That makes this a pdf and not a cdf.

 

If you are computing by hand, use the formula Kenneth gave you.  If you are using a TI-84 of some variety, you look for something like binompdf (10, 0.2, 3)

 

I hope this helps!

Answer 2

REVISED ANSWER: 10C3 TIMES 0.2^3 TIMES 0.8^7 because there are several ways of choosing the exact 3 questions that will be correct; prob of correct is 0.2 (three of them); prob of wrong is 0.8 (seven of the questions. Sorry I was wrong in an earlier version.