In an increasingly data-driven world, it is more important than ever for students as well as professionals to better understand basic statistical concepts. 100 Questions (and Answers) About Statistics addresses the essential questions that students ask about statistics in a concise and accessible way. It is perfect for instructors, students, and practitioners as a supplement to more comprehensive materials, or as a desk reference with quick answers to the most frequently asked questions.

# What Is the Correlation Coefficient, and How Is It Used?

### What Is the Correlation Coefficient, and How Is It Used?

You already know that most collections of data can be described using a measure of central tendency, such as the mean, and a measure of variability, such as the standard deviation. Sometimes, however, it is important to be able to describe the relationship between two or more variables.

The correlation coefficient, also known as the Pearson product-moment correlation coefficient (named after Karl Pearson), is a numerical index that reflects the relationship between two variables such as X and Y.

It is represented by the symbol rxy, and it ranges in value from –1.00 to +1.00. Perhaps the most-frequently made error regarding the correlation coefficient is that absolute value is more significant than the sign. For example, ...