How is a correlation of exactly -1 interpreted?

A correlation of exactly -1 indicates a perfect downhill linear relationship between two variables. This means that as one variable increases, the other variable decreases in a perfectly predictable manner. This precise negative correlation implies that every increase in the first variable results in a proportional decrease in the second variable, demonstrating a consistent and exact inverse relationship.

In practical terms, if you were to plot this relationship on a graph, all data points would lie perfectly on a straight line that slopes downward from left to right. Understanding this concept is crucial because it highlights the strength and direction of a linear relationship; hence, it exemplifies a situation where one variable can be precisely predicted based on the value of the other.