This document defines correlation as the relationship between two variables and how they depart from independence. It provides examples of correlational research questions about the relationship between time spent on homework and grades or junk food in schools and obesity. While correlation suggests an association, it does not prove that one variable causes the other. The example of past beliefs about ulcers being caused by stress and spicy foods is given, but researchers now know ulcers are actually caused by H. pylori bacteria. Correlation research can help design better experimental studies to understand causation.

1. Correlation Research: A Brief Introduction Colleen Carmean

2. Definition of Correlation correlation (or co-relation) refers to the departure of two variables from independence. (Wikipedia) What goes with, is associated with, or connects to what?

3. Examples? Is there a relationship between amount of time spent on homework and grades? What is the association between junk food sold in cafeterias and obesity in high school students in Arizona?

4. What words suggest correlation? What is the relationship… Is there an association between… Can we determine a predictive ability of…

5. Does this mean one of the variables is causing the other? Does junk food cause obesity in high school students? Does amount of time doing homework create good grades?

6. NO!

7. Researchers don’t jump to conclusions.

8. Well, sometimes we do…but we try not to. Example: Ulcers.

9. Causation? We used to believe that ulcers were caused by stress and spicy food.

10. Causation There was a correlation between the independent variables (stress/spicy food) , and the dependent variable (ulcers) but the independent variables were NOT the cause. We now know that ulcers are caused by a corkscrew-shaped bacterium Helicobacter pylori ( H. pylori ).

11. Correlation Natural stomach acids and spicy food may have irritated the already damaged stomach and small intestine, but they never caused the ulcers. For more information on ulcers, see http://www.cnn.com/HEALTH/library/DS/00242.html

12. Causation Correlation studies help us determine the existence of a relationship between variables. This relationship can help us design more precise, experimental studies to better understand our environment and causation.

13. Interested in learning more? Visit Wikipedia: Correlation Implies Causation.

14. Thank You! [email_address]