Final Selected Model

Gradient Boosting · 50 estimators · maxDepth=3 · lr=0.1

What you'll see here

Chosen for the best F1 / AUC balance without severe overfitting. Trained on a 5,000-row stratified subsample of the original imbalanced training data.

Rationale

Gradient Boosting sequentially corrects previous errors and typically produces the best AUC on tabular data with mixed feature types. Shallow trees (depth=3) with a small learning rate (0.1) trade some training-set accuracy for better generalization.

We chose original (non-resampled) training data because the base rate (33% Denied) is not extreme enough to require SMOTE-like intervention, and resampling here traded precision for marginal recall gains without improving F1 (see Resampling page).

Decision logic — depth-3 surrogate tree

Depth-3 surrogate decision tree fitted to the tuned gradient boosting model, splitting first on education, then job experience and continent

A readable stand-in for the ensemble: the first split is education (High School vs everything else), then prior job experience and continent — mirroring the importance ranking above. On held-out cases the surrogate reaches 57.44% F1 and 71.76% recall, so it is a faithful approximation of the deployed model rather than a separate story.

Business rules in plain English

Highest denial risk

Education = High School AND Applicant from Asia AND Role outside the Midwest

72.3% denied · 494 test cases

Education above High School AND No prior job experience AND Wage not quoted yearly

69.6% denied · 378 test cases

Education = High School AND Applicant from Asia AND Role in the Midwest

64.2% denied · 176 test cases

Education = High School AND Applicant not from Asia AND No prior job experience

63.4% denied · 142 test cases

Highest certification likelihood

Education above High School AND Has prior job experience AND Education = Master's

89.4% certified · 1,676 test cases

Education above High School AND Has prior job experience AND Education below Master's

75.1% certified · 2,163 test cases

Education above High School AND No prior job experience AND Wage quoted yearly

63% certified · 2,419 test cases

Education = High School AND Applicant not from Asia AND Has prior job experience

46.4% certified · 196 test cases