## Graph Data

A bar graph can be used to display data that can be counted. Here the objects or categories are listed along the horizontal axis and the associated numerical value is indicated by the length of a bar above the category. A vertical axis provides a scale for converting the length of the bar into a number.

For example, the fact that John counted 70 cars, Mary counted 60 cars, and Jim counted 45 cars can be represented by the following bar graph.

A double bar graph is used to compare two sets of data. On a vertical bar graph, objects or categories are listed along a horizontal axis and the associated numerical value is indicated by the length of a bar above each category.

A line plot is closely related to a bar graph. Line plots tend to be used when the data are categorical. A mark, X, is used to represent each object corresponding to a particular category. If a bowl of fruit contains 3 apples, 5 plums, and 2 oranges, then the corresponding line plot takes the following form.

**Teaching Model 15.2:**
Circle Graphs