Understanding Correlation

This exercise is best to complete if you have read (a) the correlation section of the statistics page and (b) the correlational studies section of the descriptive and correlational research methods page.

If you have not checked these out you can go to either or both of these pages.

Correlational studies

Statistics: Correlation

INSTRUCTIONS
Read each of the descriptions below. Then determine whether the relationship described suggests a positive or negative correlation (the section on "statistics: correlation" will review what is meant by Positive and Negative correlation). Then consider why we might find this relationship. The more you think about the correlation suggested the more possible explanations for this relationship you are likely to find. This highlights why causality cannot be established through correlational research. (The section on correlational studies reviews this idea).

A researcher finds that students who attend fewer classes get poorer grades.

Is this a positive or negative correlation?
Why might we find a relationship between attendance and grades?

Answer

Cities with more stores selling pornography have higher rates of violence.

Is this a positive or negative correlation?
Why might we find a relationship between attendance and grades?

Answer

The longer couples have been together the more similar they are in their attitudes and opinions.

Is this a positive or negative correlation?
Why might we find a relationship between attendance and grades?

Answer

Moral of the Lesson:

In each case above there was more than one explanation for why we might find the relationship between the variables. Since we cannot rule out these alternative explanations, we cannot conclude that changes in one variable "caused" changes in the other variable.

The snappy phrase to express this idea is: CORRELATION does not equal CAUSATION

BACK to Statistics Page

BACK to Research Index