Creating a scatter plot

It’s not easy to identify patterns and trends between weight and SBP by looking at a table like Table

16-1. You get a much clearer picture of how the data are related if you make a scatter plot. You would

place weight, the independent variable, on the X axis, and SBP, the dependent variable, on the Y axis,

as shown in Figure 16-3.

© John Wiley & Sons, Inc.

FIGURE 16-3: Scatter plot of SBP versus body weight.

Examining the results

In Figure 16-3, you can see the following pattern:

Low-weight participants have lower SBP, which is represented by the points near the lower-left

part of the graph.

Higher-weight participants have higher SBP, which is represented by the points near the upper-

right part of the graph.

You can also tell that there aren’t any higher-weight participants with a very low SBP, because the

lower-right part of the graph is rather empty. But this relationship isn’t completely convincing, because

several participants in the lower weight range of 70 to 80 kg have SBPs over 125 mmHg.