# Data Mining | Week 3

## Data Mining Week 3 Answers

Q1. Internal nodes of a decision tree correspond to:

A. Attributes
B. Classes
C. Data instances
D. None of the above

Q2. In a multiclass classification problem, Bayes classifier assigns an instance to the class corresponding to:

A. Highest aposteriori probability
B. Highest apriori probability
C. Lowest aposteriori probability
D. Lowest apriori probability

3. Three identical bags contain blue and yellow balls. The first bag contains 3 blue and 2 yellow balls, the second bag has 4 blue and 5 yellow balls, and the third bag has 2 blue and 4 yellow balls. A bag is chosen randomly and a ball is chosen from it. If the ball that is drawn out is blue, what will be the probability that the second bag is chosen?

A. 15/62
B. 27/62
C. 10/31
D. None of the above

Q4. What is the entropy of the dataset?

A. 0.50
B. 0.94
C. 1
D. 0

Q5. Which attribute would information gain choose as the root of the tree?

A. Age
B. Income
C. Student
D. Credit_rating

Q6. Whether a person will buy if (Age=35, Student-No, Income Low, Credit_rating = Fair)?

A. Yes
B. No
C. The example can’t be classified
D. Both classes are equally likely

Q7. What class does the person(Age-42, Student-No, Income-Medium, Credit_rating = Excellent)?

A. Yes
B. No
C. The example can’t be classified
D. Both classes are equally likely

Q8. What class does the person (Age 25, Student-No, Income-Medium, Credit_rating = Fair}?

A. Yes
B. No
C. The example can’t be classified
D. Both classes are equally likely

Q9. Which attribute would information gain choose for Age=31-40?

A. Student
B. Income
C. Is a leaf node with value Yes.
D. Credit_rating 0 