A line can look dramatic or nearly flat depending on the range shown by the chart. Before interpreting the shape, read the axis labels, units, and scale.
Check whether intervals represent equal steps and whether the chart uses a transformed scale. A narrowed range can reveal a small variation, but the reader needs enough context to understand its size. The right presentation depends on the comparison being made.
Ask what the chart would look like under another reasonable range. The purpose is not to require every chart to use the same starting point, but to recognize the choices that affect the visual impression. A useful chart makes those choices legible.
- Read units and scale first.
- Check the range being shown.
- Compare the visual impression with the actual difference.
A small working example.
Imagine two charts covering different time spans. Their slopes cannot be interpreted fairly without reading the horizontal axes first.
A note to keep beside it.
A column name can hide an assumption. Check units, missing values, and the counting rule before combining observations that only appear to be alike.
Follow a related question
Write the assumptions beside the calculation.
An estimate with visible assumptionsAsk which situations the examples cover.
Examples shape the model’s taskKeep learning
Related background to continue exploring this subject.
NIST: statistical engineering W3C: accessibility, usability, and inclusion
