Multi-variable data plotted on axes starting from the same center point.

A radar (web) chart has one axis for each variable, all radiating from a common center. The value on each axis is marked and neighbouring marks are joined, forming a polygon. It is useful for comparing the overall profile of one or more items across several criteria.

Reading a radar chart

• Each spoke is a separate variable; the distance from the center gives its value.
• Use the concentric rings as the scale, and check the maximum value of each axis.
• A larger polygon means higher values overall; a point near the center means a low value on that variable.
• When several polygons are drawn, use the legend to tell the series apart.

Common calculations

• Total or average score: sum of the values on all axes, or that sum divided by the number of axes.
• Difference between series: subtract their values on the same axis.
• Percentage of the maximum: value / axis maximum x 100.
• Weighted score: sum of (value x weight) divided by the sum of the weights.
• Strongest and weakest areas: the highest and lowest points of a polygon.

How to solve questions

1. Identify the series and axes the question refers to.
2. Read each value carefully using the ring scale.
3. Apply the required sum, average, difference, or percentage.
4. Check that the answer is consistent with the shape of the polygon.