Section 9.4: Choosing a Data Display

Property

Choose data displays based on data type and purpose: categorical data $\rightarrow$ bar graphs or circle graphs; numerical data over time $\rightarrow$ line graphs; numerical data distribution $\rightarrow$ histograms, dot plots, or box-and-whisker plots; relationship between two variables $\rightarrow$ scatter plots; ordered numerical data $\rightarrow$ stem-and-leaf plots.

Examples

Property

We can use a bar graph to display the values of a variable. The height of the bar illustrates the value at each time or in each situation. A double bar graph can be used to compare the values of two different variables under the same conditions.

Examples

• A bar graph shows daily screen time. On Monday, the bar reaches 3 hours. On Wednesday, it reaches 2 hours. This means screen time was 1 hour longer on Monday than on Wednesday.

• A double bar graph compares the number of goals scored by Team A and Team B. In the first game, Team A's bar is at 4 and Team B's is at 2. Team A scored 2 more goals.

Property

Circle graphs (pie charts) display data as sectors of a circle where each sector represents a part of the whole. The central angle of each sector is proportional to the data value: $\text{Central Angle} = \frac{\text{Data Value}}{\text{Total}} \times 360°$

Examples