Definition
Graph scale
A graph scale tells how much the value changes from one marked position to the next on an axis.
What it means
The spaces on an axis do not automatically mean 1. Read two labelled marks and find their difference. That difference is the value of one equal interval between them. Use the same interval all along that axis. Then check the other axis separately because it may use a different scale.
Remember it
One equal step, one equal value jump.
Example
A vertical axis is labelled 0, 25, 50, 75, and 100 at equal distances. Each interval represents 25. A bar ending at the fourth marked level represents 75, not 4, because the labels—not the number of marks—set the scale.
Watch for
Do not assume each tick mark means 1; the labelled values determine the interval, and any break or change must be shown explicitly.
Common mix-up
Graph scale maps axis steps to values; scale factor multiplies one size to make another.
Exact meaning
A graph scale is the rule connecting positions on an axis to numerical values. On the linear graphs used in this age range, equal distances represent equal numerical intervals on the same axis, although the horizontal and vertical axes may use different intervals.