The purpose of this lesson is to get students thinking about what makes a “good” graph by considering components such as labels and scale. Students add a scale to graphs showing the pace of two bugs and graph an additional line based on a verbal description of a third bug (MP2).

This lesson includes graphs with elapsed time on the vertical axis and distance traveled on the horizontal axis. In general, a context that involves a relationship between two quantities does not dictate which quantity is the independent or dependent variable. Consider this situation where a runner is traveling one mile every 10 minutes.

• We can say the number of miles traveled, , depends on the number of minutes that have passed, , and write . This way of expressing the relationship might be more useful for questions like "How far does the runner travel in 35 minutes?"
• We can also say that the number of minutes that have passed, , depends on the number of miles traveled, , and write . This way of expressing the relationship might be more useful for questions like "How long does it take the runner to travel 2 miles?"

Both interpretations have meaning, and both could be of interest—it is up to the modeler to decide what questions they want to answer about the context and which way of expressing the relationship will be most useful in answering those questions.