Free SOA Exam PA (Predictive Analytics) Tree-Based Models Practice Questions
Tree-based models on SOA Exam PA cover decision trees, random forests, and gradient boosting machines: reading fitted trees and variable importance plots, tuning parameters, and weighing interpretability against predictive performance.
75 questions16 easy52 medium7 hard2026 syllabus
Sample Questions
Question 1
Easy
Which statement best describes the fundamental difference between boosting and bagging for tree ensembles?
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Correct Answer: B
Solution
B is correct. Boosting is a sequential procedure: each new (typically shallow) tree is fit to correct the mistakes of the ensemble built so far, chiefly reducing bias. Bagging fits many independent trees on bootstrap resamples and averages them, chiefly reducing variance.
Question 2
Medium
In rpart.control, which statement correctly matches a control parameter to its effect on tree growth?
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Correct Answer: C
Solution
C is correct. minbucket sets the minimum number of observations permitted in a leaf. cp is the minimum improvement in the (scaled) fit required to make a split, minsplit is the minimum node size before a split is attempted, and maxdepth caps tree depth. Lowering cp permits more splits, producing a larger, not smaller, tree.
Question 3
Hard
A GBM and a random forest are both fit to the same claims dataset. Which statement about their bias-variance behavior is most accurate?
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Correct Answer: C
Solution
C is correct. Random forests average many decorrelated high-variance trees, so their gain is variance reduction. Boosting sequentially reduces bias by targeting residuals, and because it keeps adding corrective trees it can overfit when the learning rate, depth, or number of rounds are not tuned.
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