Displaying data with two variables

When investigating the relationship between two quantitative variables we draw a scatterplot.

• When drawing a scatterplot the convention for plotting graphs applies.
• The independent variable is placed on the horizontal axis.
• The dependent variable is placed on the vertical axis.
• When looking at the graph, you need to consider the:
  • Form — does it resemble a straight line or another type of function?
  • Direction — if it is resembles a straight line, what direction is it going (positive — up, or negative — down)
  • Scatter — are the points scattered close to a line or do they have a large scatter?
• If the relationship appears to be a straight line you can draw a line of best fit.