Correlation coefficient
MCAT glossary · Critical Analysis & Reasoning Skills
Definition
A number from -1 to +1 quantifying the strength and direction of a linear relationship.
Correlation coefficient in plain English
A correlation coefficient is a single number that tells you how tightly two things move together, on a scale from -1 to +1. A value near +1 means they rise together (more studying, higher grades); near -1 means one goes up as the other goes down (more absences, lower grades); and near 0 means basically no straight-line relationship. The SIZE tells you how strong (how close the dots hug a straight line) and the SIGN tells you the direction. One catch: it only measures STRAIGHT-line patterns, and a strong correlation still doesn't prove one thing causes the other.
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