What is wrong with truncating the y-axis on a bar chart of similar values?
PICTURE THIS: HOW TO EXPLAIN IT
Simple meaning
Starting bars above zero exaggerates small differences and violates the expectation that bar length maps to magnitude.
WHY — Visualization instead of guessing?
Why interviewers care about Visualization:
who only read docs from people who shipped.
and tied to Data Science work.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Starting bars above zero
exaggerates small differences and violates the expectation that bar length maps to magnitude.
- 2It is a common
dashboard trick that makes a 1 percent gap look like a doubling.
- 3If you must zoom,
use a line with a clearly labeled axis and show the full-scale inset.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Starting bars above zero exaggerates small differences and violates the expectation that bar length maps to magnitude. It is a common dashboard trick that makes a 1 percent gap look like a doubling.