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- Short video first, then we unpack it
- Goal: a checklist you can run on any chart — in the news, at work, or in your own reports
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- Click "Play on TED" — opens in the browser; go full screen
- Ask the class to jot down each trick as it appears
- After the video: quick round — "which trick surprised you most?"
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- We trust pictures more than tables — our eyes do the maths for us, and that is the weakness
- The video's point: the problem is not graphs, it is how they are built
- Most misleading charts you meet at work are accidents, not lies — but the damage is the same
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- The video's example: a truck ad where the axis started near 95%, so one brand looked far ahead
- Ask: on the left, how much more reliable does Brand A look? (2–3×). Real gap: ~2 points
- Rule: bar and column charts start at zero. Line charts may zoom in — but say so clearly
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- The video lists both axes: y-axis not starting at zero, x-axis skipping intervals, scales left out
- Uneven x-axis makes growth look smoother or sharper than it was
- Quick habit: read the axis labels before you look at the shape
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- An eye-catching unit (stacks of cash, football fields) feels meaningful but rarely helps a decision
- 3D pies: slices at the front look bigger than the same slice at the back
- Dual-axis charts: you can make almost any two lines cross by choosing the axis ranges
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- The video's example: a weather chart that compared a dry spell only with the last few years, so it looked like near-record — older years had a longer streak
- That one was probably careless, not dishonest — someone just picked a short date range
- Ask of every time chart: why does it start *here*? What happens if I go further back?
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- The flip side of the truncated axis: a huge range flattens a small change that is still important
- Here, under one degree looks like nothing on the left — but for climate it is a big shift
- Ignored variables: "crime went up" — did population go up too? Show per-capita
- So "always start at zero" is not the whole rule; the right scale depends on what change matters
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- Source check is the cheapest and fastest test
- At work: whose dashboard is it, and what are they measured on?
- Before forwarding a chart: can you name the original data source?
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- Turn the lens around: the most common misleading chart you will see this year might be your own
- Excel / Power BI pick axis ranges automatically — and often not from zero
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- Source: Mahbub et al., "The Perils of Chart Deception", IEEE VIS 2025 — 800 chart pairs, 8 trick types, 16,000+ answers
- Models were 2025 versions (GPT-4o, Gemini 2.5 Pro, Claude 3.7 Sonnet, plus open-source models) — newer ones may do better, but the lesson holds
- Gemini 2.5 Pro was the most robust: fooled by 3 of 8 trick types; spotted the upside-down axis in 79% of cases
- None of the open-source models mentioned the upside-down axis in their answers
- Upside-down axis: higher values plotted lower, so a rise looks like a fall — not covered in the video, but worth adding to the checklist
- Ask: who has pasted a chart into ChatGPT / Claude and asked "what does this show"?
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- Seven quick questions — takes under a minute per chart
- Pair exercise: find one chart in today's news and run the checklist together
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- If they remember one thing: read the axes before the shape
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- The TED-Ed lesson page has a short quiz and discussion questions — good homework
- Huff is old but still the most readable book on the topic
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- Ask: "Name a chart you've seen at work that failed one of the checks"
- Link back to the Dashboard Design deck: same rules apply when you build your own reports