# >Plot States with Bar Charts & Pie Graphs

#### How to Use: Skim the examples to gain inspiration for different Plot States (graphical displays) you can create for the lessons you author or that you can have students create in the course of a lesson. Bar charts of values and means are good for comparing quantitative data. Stretched Bar Charts and Pie charts are good for representing proportions.

Example One: Bar Chart of Values

A bar chart of values is a type of graph in which the bars represent the value of an individual case. The example below shows the dinosaurs categorized by hip type.  Each case is shown as a bar, with the bar length representing the length of each individual dinosaur. Colors in the Legend indicate the dinosaurs' respective diets.

Example Two: Stretched Bar Chart

A stretched bar chart compares proportions within a group. Each bar is of equal length, with subsection lengths indicating each category's contribution to the group.

The bar chart below categorizes dinosaurs by geologic period. The stretched bars show the percentage of the dinosaurs in each category that had bird-like or lizard-like hip structure.

*Note that each bar stretches to 100% of the dinosaur population at that time, so this bar chart may not be used to compare the overall number of dinosaurs in each geologic period, only the relative proportions of hip type within a geological period.

Example Three: Bar Chart of Means

The bar chart of means allows you to visualize the mean of a quantitative attribute. In the example below, the dinosaurs are categorized by their number of legs. It then shows the mean weight of any dinosaurs that fall into the category.  In this instance, we have made the labels visible by choosing Stats>Mean and then Stats>Show Labels.

Example Four: Pie Graphs

A pie graph displays combined totals for various categories rather than individual cases. It's useful for understanding how each category contributes to the overall total in terms of percentage.

The pie graph below shows the proportion of dinosaurs with each diet type.