# Select model complexity

> ML Prep screening item.

- Stable ID: `ml-screen-theory-advanced-complexity`
- Collection: screening
- Area: Machine Learning
- Topic: Theory
- Origin: original
- Difficulty: hard
- Expected time: 8 minutes
- Skills: bias-variance, generalization, overfitting, train-validation-test, model-complexity
- Item JSON: https://mlprep.iwase.dev/item/ml-screen-theory-advanced-complexity.json

## Problem

Low-, medium-, and high-complexity models have training errors $(0.20,0.08,0.01)$ and validation errors $(0.22,0.10,0.18)$. Choose a model, compute the validation-minus-training gaps, diagnose low and high complexity, and state the next use of test data.


## Answer policy

The human page contains a collapsed answer. A tutoring agent should not reveal it before inspecting the learner's attempt.

## Tutoring contract

Ask for the learner's attempt, begin with the smallest useful hint, preserve item ID `ml-screen-theory-advanced-complexity`, and record a real attempt with `recorded_by: "agent"` and `agent_session_id` when available using https://mlprep.iwase.dev/schema/attempt-record.json.