# Classification metrics from counts

> ML preparation item.

- Stable ID: `original-ml-metrics`
- Area: Machine Learning
- Topic: Classification
- Origin: original
- Expected time: 6 minutes
- Skills: confusion-matrix, precision-recall, decision-boundary
- Item JSON: https://mlprep.iwase.dev/data/items/original-ml-metrics.json

## Problem

A classifier has $\mathrm{TP}=30$, $\mathrm{FP}=10$, $\mathrm{FN}=20$, and $\mathrm{TN}=40$. Compute accuracy, precision, recall, and $F_1$.


## Answer policy

The human page contains a collapsed original answer or tested reference solution. 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 `original-ml-metrics`, and record a real attempt with `recorded_by: "agent"` and `agent_session_id` when available using https://mlprep.iwase.dev/schema/attempt-record.json.