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# Machine Learning Questions & Answers

11. Which of the following is a widely used and effective machine learning algorithm based on the idea of bagging?

A. Decision Tree
B. Regression
C. Classification
D. Random Forest

12. To find the minimum or the maximum of a function, we set the gradient to zero because:

A. The value of the gradient at extrema of a function is always zero
B. Depends on the type of problem
C. Both A and B
D. None of the above

13. Which of the following is a disadvantage of decision trees?

A. Factor analysis
B. Decision trees are robust to outliers
C. Decision trees are prone to be overfit
D. None of the above

14. How do you handle missing or corrupted data in a dataset?

A. Drop missing rows or columns
B. Replace missing values with mean/median/mode
C. Assign a unique category to missing values
D. All of the above

15. When performing regression or classification, which of the following is the correct way to preprocess the data?

A. Normalize the data -> PCA -> training
B. PCA -> normalize PCA output -> training
C. Normalize the data -> PCA -> normalize PCA output -> training
D. None of the above

16. Which of the following statements about regularization is not correct?

A. Using too large a value of lambda can cause your hypothesis to underfit the data.
B. Using too large a value of lambda can cause your hypothesis to overfit the data
C. Using a very large value of lambda cannot hurt the performance of your hypothesis.
D. None of the above

17. Which of the following techniques can not be used for normalization in text mining?

A. Stemming
B. Lemmatization
C. Stop Word Removal
D. None of the above

18. In which of the following cases will K-means clustering fail to give good results?
1) Data points with outliers
2) Data points with different densities
3) Data points with nonconvex shapes

A. 1 and 2
B. 2 and 3
C. 1 and 3
D. All of the above

19. Which of the following is a reasonable way to select the number of principal components "k"?

A. Choose k to be the smallest value so that at least 99% of the varinace is retained.
B. Choose k to be 99% of m (k = 0.99*m, rounded to the nearest integer).
C. Choose k to be the largest value so that 99% of the variance is retained.
D. Use the elbow method.

20. What is a sentence parser typically used for?

A. It is used to parse sentences to check if they are utf-8 compliant.
B. It is used to parse sentences to derive their most likely syntax tree structures.
C. It is used to parse sentences to assign POS tags to all tokens.
D. It is used to check if sentences can be parsed into meaningful tokens.