An Introduction to Artificial Intelligence Week 5

Course Name: An Introduction to Artificial Intelligence

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These are An Introduction to Artificial Intelligence Answers Week 5


Q1. Which of the following statements are true in the context of alpha-beta pruning?
a. The effectiveness of alpha-beta pruning depends on the order of moves encountered during the search
b. A node is pruned if beta >= alpha at one of it’s parents
c. A node is pruned if alpha >= beta at one of it’s parents
d. Alpha-beta pruning can result in a different root value from full minimax search

Answer: a, c


These are An Introduction to Artificial Intelligence Answers Week 5


Q2. The next three questions will involve the following search tree. The value of the leaf nodes are annotated below the node in the diagram.

image 66

What is the backed-up value at the root node after minimax search?

Answer: 20


These are An Introduction to Artificial Intelligence Answers Week 5


Q3. Assume that the successors are expanded from left to right. What is the number of nodes (including leaf nodes) pruned by alpha-beta pruning?

Answer: 12


These are An Introduction to Artificial Intelligence Answers Week 5


Q4. Assume that the successors are expanded from right to left. What is the number of nodes (including leaf nodes) pruned by alpha-beta pruning?

Answer: 3


These are An Introduction to Artificial Intelligence Answers Week 5


Q5. Which of the following is true regarding fixed depth search and the horizon effect?
a. Continuing the search at non-quiescent positions can mitigate the horizon effect
b. Stopping the search at non-quiescent positions can mitigate the horizon effect
c. It can lead to choosing moves with short-term benefits, but catastrophe in the long term
d. It can result in ignoring moves that do not have immediate benefits, but can lead to victory in the long term

Answer: a, c, d


These are An Introduction to Artificial Intelligence Answers Week 5


Q6. Which of the following games are deterministic?
a. Backgammon
b. Go
c. Bridge
d. Othello

Answer: b, d


These are An Introduction to Artificial Intelligence Answers Week 5


For Questions 7 to 10 –  

Aman and Bharat are two friends. Aman is planning an ice-cream treat. They are not able to decide the location, brand and the flavour to be purchased. Therefore, they come up with the following idea: First, Aman gets to choose the location between Hauz Khas and Connaught Place, then Bharat chooses the brand between Giani’s and Nirula’s and then the flavour is chosen uniformly randomly between chocolate and vanilla. The table below lists the cost of each ice-cream in rupees for a particular location, brand and flavour.

image 67

Additionally, Aman wants to get by with spending as less money as possible, while Bharat wants to get the most expensive treat he can get out of Aman, both in expectation. Let’s model this as a minimax tree with chance nodes and run expecti-minimax search.

Q7. If both Aman and Bharat choose optimally and selfishly, which of the following statements are correct?
a. They go to the location Connaught Place.
b. They buy from the brand Nirula’s.
c. They go to the location Hauz Khas.
d. They buy from the brand Giani’s

Answer: a, d


These are An Introduction to Artificial Intelligence Answers Week 5


Q8. If both the players play optimally, determine the expected expenditure in rupees.

Answer: 40


Q9. Which of the following statements are true for the expecti-minimax tree and alpha beta pruning for the problem?
a. There are 4 chance nodes in the expecti-minimax tree.
b. Some nodes get pruned even if alpha beta pruning is employed with the worst possible node ordering
c. Some nodes get pruned if alpha beta pruning is employed with the best possible node ordering.
d. The choice of location and brand depends upon the order of nodes explored.

Answer: a, c


These are An Introduction to Artificial Intelligence Answers Week 5


Q10. Suppose the order of decisions is changed as follows: First Bharat chooses the brand between Giani’s and Nirula’s, then Aman gets to choose the location between Hauz Khas and Connaught Place, and then the flavour is chosen uniformly randomly between chocolate and vanilla. If both decide optimally, which of the following statement is correct about the new expected expenditure(E’) compared to the expected expenditure in the original case(E)?
a. E’ = E
b. E’ > E
c. E’ < E
d. Cannot be determined

Answer: c. E’ < E


These are An Introduction to Artificial Intelligence Answers Week 5



These are An Introduction to Artificial Intelligence Answers Week 5

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These are An Introduction to Artificial Intelligence Answers Week 5

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