1. Rules for Graphing

2. Rules for Graphing
Identify the Independent and Dependent Variables.

3. Independent vs. Dependent Variables
Independent Variable – the variable that the experimenter controls
Dependent Variable – the variable that changes as the independent variable changes

4. Rules for Graphing
2. Determine the range of the independent variable to be plotted.

5. Rules for Graphing
3. Decide whether the origin (0,0) is a valid data point.

6. Rules for Graphing
4. Spread the data out as much as possible. Let each division on the graph paper stand for a convenient unit.

7. Rules for Graphing
5. Number and Label the Horizontal Axis.

8. Rules for Graphing
6. Repeat steps 2-5 for the Dependent Variable.

9. Rules for Graphing
7. Plot the Data Points on the Graph.

10. Rules for Graphing
8. Draw the “best fit” straight line or smooth curve that passes through as many data points as possible (Do not connect the dots).

11. Rules for Graphing
9. Give the graph a title that clearly tells what the graph represents.

12. Data Analysis
Identify relationships between variables from a Data Table, Graph or both.

13. Graphical Relationships
Linear (Direct Proportion)
Parabolic (Exponential)
Inverse (Hyperbolic)

14. Linear Relationships
Look for a constant rate of increase or decrease in both variables.
y = mx + b

15. Linear Relationships m = slope = rise/run
y – intercept = the “y” coordinate where x = 0

16. Parabolic Relationship
Look for a varying rate of increase of one variable w.r.t. the other variable.
y = kx2
k = the rate of increase of the variables.

17. Inverse Relationships
Look for a varying rate of decrease in one variable as the other variable increases
xy = k or y = k/x
k is a constant that shows the rate of decrease between the variables.
DO NOT CONFUSE WITH LINEAR WITH A NEGATIVE SLOPE!