1. Graphs and Graphing Data
Biology

2. Experimental Variables
Variable: A factor in an experiment.
Independent variable: The factor that is different between groups. The topic of interest in an experiment-because you expect it to cause a change in the experiment.
Has two or more levels.
Levels can be numbers (age, weight, etc.) or categories (gender, color, etc.)
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

3. Experimental Variables
Variable: A factor in an experiment.
Independent variable: The factor that is different between groups. The topic of interest in an experiment-because you expect it to cause a change in the experiment.
On graphs, the independent variable always goes on the X-axis.
Fig. 1
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

4. Experimental Variables
Variable: A factor in an experiment.
Dependent variable: The factor being measured in the experiment.
Almost always numerical
On graphs, the dependent variable is always on the Y-axis.
Fig. 1
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

5. Types of Graphs Two common types of graphs used in science: Bar graphs
Line graphs
Fig. 2
Fig. 3
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

6. Types of Graphs
Bar graphs are used when the independent variable has categories.
Boys/girls
Adults/children
Salt water/distilled water /tap water
Etc.
Fig. 2
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

7. Types of Graphs
Line graphs are used when the independent variable has numbers.
Hours of television watched
Age (in years)
Calories eaten per day
Etc.
Both line graphs and bar graphs show the relationship between independent variables and dependent variables.
Fig. 3
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

8. Making a Graph
Choose a scale for each axis that includes all values. Number your gridlines evenly.
Fig. 1
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

9. Making a Graph Label both axes, including units. Fig. 1
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

10. Making a Graph Plot each data point and connect your dots with a line.
Fig. 1
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.

11. Making a Graph Give your graph a descriptive title. Fig. 1
Derby, S. (2004) Graphs and Graphing PowerPoint Presentation.