A pie graph (or pie chart) is a specialized graph used in statistics. The independent variable is plotted around a circle in either a clockwise direction or a counterclockwise direction.The dependent variable (usually a percentage) is rendered as an arc whose measure is proportional to the magnitude of the quantity.Each arc is depicted by constructing radial lines from its ends to the center of the circle, creating a wedge-shaped "slice."The independent variable can attain a finite number of discrete values (for example, five).The dependent variable can attain any value from zero to 100 percent.
The illustration is a pie graph depicting the results of a final exam given to a hypothetical class of students.Each grade is denoted by a "slice."The total of the percentages is equal to 100 (this is important; if it were not, the accuracy of the graph would be suspect).The total of the arc measures is equal to 360 degrees.