What does a correlation coefficient of -1 signify?

A correlation coefficient of -1 signifies a perfect negative association between two variables. This means that as one variable increases, the other variable decreases in a perfectly linear manner. The relationship is not just strong; it is the strongest possible negative relationship that can exist, indicating that there is a consistent and predictable inverse relationship between the two variables.

In practical terms, this could be represented visually on a scatter plot as a straight line sloping downward from left to right. Each move in either variable directly affects the other in the opposite direction without any exceptions. This contrasts greatly with a positive correlation, where an increase in one variable results in an increase in the other, and with no correlation, where variations in one variable do not predict any changes in the other.