Why is a scatter plot an appropriate type of graph for presenting the data from the second experiment?

• A. The dependent variable is categorical.
• B. The independent variable is categorical.
• C. Both the dependent variable (percentage reduction in swimming speed) and the independent variable (time since first exposure to cane toads) represent continuous numerical data.
• D. It shows a distribution.

Answer: (C)

The data involve two quantitative measurements: time since first exposure (continuous) and the percentage reduction in swimming speed (continuous). A scatter plot pairs these two numbers for each observation, placing time on the horizontal axis and the speed-change on the vertical axis. This setup is ideal for examining how one continuous variable relates to another—you can see trends, whether speed reduction tends to increase or decrease as time passes, and spot any outliers or unusual patterns. If one variable were categorical, a scatter plot wouldn’t be the best choice; you’d use bar graphs or box plots instead. A scatter plot is not primarily a display of distribution; that’s better shown with histograms or box plots, though a scatter plot can reveal how spread varies across the range of the independent variable.