Check AI chart reading with one misleading axis

A bar chart can lie without a single wrong number. This guide gives you one: bars of 98% and 100% on an axis that starts at 96, so a 2-point gain looks like a doubling. You'll build the exact chart I used, run it on Claude Sonnet 5.5 and Claude Opus 5.5 with the same two prompts, and score every answer against a fixed answer key. I ran this test on October 6, 2026, and the real prompts, answers and scorecard are below as the worked example. It's for anyone who hands Claude dashboards, reports or screenshots and wants to know how far to trust the read.