Scatter diagrams look at a possible correlation between two sets of data, such that when one set changes, you would expect the other set to change as well.
Scatter graphs enable correlations between disease and lifestyle choices, and correlations between disease and environmental or industrial conditions, such as possible effects of pesticides, industrial chemicals, etc.
The scatter graph below uses data from a landmark scientific paper of 1975, where Ken Carroll investigated women eating different amounts of animal fat and deaths from breast cancer.