---
id: course-da-visualization-l01
type: course
title: "Challenge 01: A chart is packaged evidence"
summary: "Say what claim each required PNG makes before writing code — the JSON summary is the auditable layer."
lang: en-US
content_version: 1
status: reviewed
reviewed_on: 2026-09-12
hints:
  - title: "What this checkpoint tests"
    body: "Charts as packaged evidence: before coding, say what claim each required PNG makes — `revenue_by_region` claims region totals, `daily_revenue` claims the trend, `revenue_histogram` claims the distribution."
  - title: "Claim before pixels"
    body: "A chart whose numbers are wrong is a lie with good typography — the JSON summary is the auditable layer the PNG must match."
  - title: "When you are done"
    body: "You can state the three claims and which aggregation feeds each."
---

# Challenge 01: A chart is packaged evidence

**Gate:** self-attested · **Points:** 10

Every chart is a claim about numbers. Before writing code, say out loud
what each of the three required charts *claims*:

- `revenue_by_region.png` claims: "region totals are X, Y, Z."
- `daily_revenue.png` claims: "the daily series looks like this."
- `revenue_histogram.png` claims: "row-level revenue is distributed
  like this."

If the claim is wrong, a beautiful chart is worse than no chart.

**Checkpoint:** you can state the claim behind each chart. Self-attested;
record via `python verify.py`.