Four friends took the final exam and the probability that each of them would get an "A" is 1/4. Use Binomial distribution (Lecture 27) to answer the following questions.

We are interested in total number of A's among these four friends.

17. What are the n and p in this (binomial) model?

• a. n=4 p=1/2
• b. n=A and p=1/3
• c. n=4 p=1/5 and k=0,1,2,3,4,..
• d. None of the above.

18. What is the probability that 3 out of 4 friends got A's on the exam?

• a.
• b. 0.046875
• c. 0.2194
• d. None of the above.

19. Which of these is the most likely to happen?

• a. None of the friends got an A.
• b. All of them got A's.
• c. Only one friend got an A.
• d. Only two friends got A's.