What does it mean if a correlation coefficient is -0.8?

A correlation coefficient of -0.8 indicates a strong negative correlation between two variables. This means that as one variable increases, the other variable tends to decrease, and this relationship is quite pronounced. In statistical terms, correlation coefficients range from -1 to 1. A value close to -1 signifies a strong negative association, while values closer to 0 indicate weaker relationships and values close to 1 represent strong positive relationships.

In this case, the -0.8 value suggests that there is a significant inverse relationship, where changes in one variable will likely result in reverse changes in the other with considerable consistency. This strong correlation is useful for predicting values; if we know one variable, we can make a fairly accurate prediction about the other due to their strong relationship.