1. Graphing

2. Why do we use graphs? It’s an organized way to express data. Allows for easy interpretation of the data. Allows for “extrapolation” of data, when necessary. What does extrapolation mean???

3. What are the parts of a graph? Independent variable: –Goes on “x” (horizontal) axis –Controlled by the experimenter – “I” for I control the independent variable! Dependent variable: “D” for Data!! –Goes on “y” (vertical) axis –Result of applying the independent variable Let’s do a practice problem!

4. Determining variables The following is a data table gathered by geologists after a volcanic eruption in Hawaii. Geologists were interested how lava affected the temperature of nearby rocks. Based on the table, what is the independent variable and what is the dependent variable? –ANS: IND = time DEP = temp Time (minutes) Rock temp (◦ C) 030 133 238 340 441 542 643 7 8 XY

5. Setting up your graph Now we know the variables, so we know where to plot them. –On X axis (independent) Time –On Y axis (dependent) Temperature

6. Time (minute s) Rock temp (◦ C) 030 133 238 340 441 542 643 7 8 Plotting Your Data

7. Interpreting your graph What is the trend in the graph we just plotted? –Temp increases then levels off. Why did it level off after 6 minutes? –Many reasons; possibly lava began to cool.

8. Types of relationships determined by graphs Direct relationship –BOTH variables (x and y) INCREASE –Can you sketch a graph that shows this?

9. Types of relationships determined by graphs Indirect relationship: –Independent variable increases, dependent decreases. –Can you sketch a graph with this relationship?

10. Types of relationships determined by graphs Cyclic relationship: –S–Shows repeating of same event over time –C–Can you sketch a graph that shows a cyclic relationship?

11. Stable (no change): –Dependent variable stays the same as independent increases –Can you sketch a graph showing stability?

12. Comparing rates of change using graphs The angle of plotted line tells us the rate –The STEEPER the line, the FASTER the rate –Which of the following graphs has a faster rate?