Correlational Study

Do people with higher education earn more money? If I spend more hours tutoring my 8-year-old daughter, will she do better in math? If I run more, will it lower my blood pressure? We ask questions such as these every day, and researchers invest their time in finding the answers—a way in which to measure the degree to which variables are related. The correlation statistic, or coefficient (r), is often used to assess whether there is a predictable association between two sets of scores. This entry briefly describes the properties of a correlation, the types of variables measured and corresponding correlational index, and the notion of correlation and causality.