prob. of getting exactly 4 correct on 20-Q multiple-choice

[HeatherBelle09]

If a student randomly guesses at 20 multiple-choice questions, what is the probability that the student gets exactly four correct. Each question has four possible choices.

 

[galactus]

This is standard binomial proability.

\(\displaystyle \L\\C(n,k)p^{k}q^{n-k}\)

If chosen at random, since there are 4 choices, there is a 25% chance of answering each question correctly

\(\displaystyle \L\\C(20,4)(0.25)^{4}(0.75)^{16}\)

The parakeet problem works the same way.

 

[HeatherBelle09]

Thank you sooooooo very much!!!!!! I understand totally how to do these now...you were such an amazing help!!!!!