Unfortunately, the examples of bad graphs on the next pages
are no longer available. After a recent web upgrade at SFU,
most of the links no longer work, and the Administration at
Simon Fraser University is unwilling to commit resources to fix
Visit these pages for a revised compendium of Bad Graphs. (look for the first bullet point under Chapter 0).
Some basic principles to follow when constructing graphs are:
The best graph is one that is self-explanatory!
There are many common errors that are made in poor graphs. Here are some
of the most common errors:
- Wrong graph type. Think about what you want to present. Trends are best displayed using lines.
Compositions best displayed using segmented-bar-charts.
- Missing text. All tick-marks and axes must be labelled. The graph needs a title.
- Inconsistent scale. The scale must be constant across the graph; don't change the increments between tick marks..
Most people read increasing scales from left to right and from bottom to top.
Comparative graphs must be plotted on the same axes to facilitate comparisons.
- Misplaced zero point. Most people assume that the zero point is at the bottom of the graph.
This can give a very misleading impression of the amount of change present in a data series.
- Poor chart effects. Shading, 3-D effects, or ducks are often added to liven up a graph.
In most cases they are useless since they distort the graph and add little new information to the story.
3-D effects are particularly poor as no information is being added; it is difficult to read the chart values;
and often the graph is also tilted to make it even harder to read the graph.
- Confusing of area and length. If you make a picture twice as large, it looks as if it has four times the area!.
- No adjustment for inflation. Dollar amounts must be adjusted for inflation. Otherwise, any comparison is misleading.
- Too much precision. We've all seen graphs reporting that the amount of money raised is $13,456,234.32.
Most people can't distinguish objects at a resolution better than one part in a hundred. Consequently, giving 10
significant digits is just silly. It would be far better to present this number as simply $13 million (i.e.
get rid of all the extra zeroes and use an appropriate scale).
Copyright 2010: Carl J. Schwarz firstname.lastname@example.org