BE VIZ SMART ✹

When you read a line graph, always check the scale.

Graph makers can make the same data look very different just by using a different scale.

Three Different Graphs, Same Data

The graphs below show how many pounds of fresh apples each person in the U.S. ate each year over ten years. The graphs show the same data, but use different scales.

1-pound scale

With this scale, small differences in value look like big changes. What do you notice about the y-axis?

2-pound scale

This is a good scale for this data set because the values range from 15 to 19

5-pound scale

With this scale, differences in value are barely noticeable, making it look like the data were flat, or didn’t change from year to year.

And increasing the maximum value on the y-axis to 30 moves all the data points down toward the center of the grid.