1. Graphs
Graph Interpretation

2. Basics of Graphs Pictorial/ visual representation of statistical data
Most graphs employ two axes:
The horizontal axis – which has the independent variable
The vertical axis – which has the dependant variable
As the name implies the independent variable determines the value of the dependant variable

3. Aspects of a Graph
Graph Title: The title appears at the top of the graph and should describe the graph.
Axis Labels: The labels that appear along the x and y-axes describing what is being measured.

4. Bar Graph Compare data points to one another.
Independent horizontal axis – shows different groups or categories
Dependant vertical axis – shows the amount of the independent variable being measured

5. Bar Graph

6. Bar Graph

7. Pie Chart Part-to-whole measure, usually a percentage
Circle is divided into sections
The size, or angle, of each sector is directly proportional to the percentage of the whole it represents.
Degrees used to be accurate. (3.6 × 100%)
Independent variable – Category/group
Dependant variable – Percentage/size of the section/angle

8. Pie Chart

9. Pie Chart

10. Broken-line graph The most common graph is a broken-line graph
Independent horizontal axis – a factor of time
Dependant vertical axis – shows the amount of the independent variable being measured
Data points are plotted on such a grid and then connected with line segments to give an approximate curve

11. Broken-line graph

12. Broken-line graph

13. When to Use . . .
. . . a Line graph.
Line graphs are used to track changes over short and long periods of time. When smaller changes exist, line graphs are better to use than bar graphs. Line graphs can also be used to compare changes over the same period of time for more than one group.

14. When to Use . . .
. . . a Pie Chart.
Pie charts are best to use when you are trying to compare parts of a whole. They do not show changes over time.

15. When to Use . . .
. . . a Bar Graph.
Bar graphs are used to compare things between different groups or to track changes over time. However, when trying to measure change over time, bar graphs are best when the changes are larger.