Statistical correlation involves using measurements on two variables to determine how they are related. Correlation coefficients range between 1.0 and -1.0, with 1.0 representing a relationship between variables where each variable moves exactly in the same direction as the other variable. A correlation coefficient of 1.0 would represent a perfect, positive relationship between two variables.
The opposite relationship is represented in the -1.0 correlation coeficient, because as one variable, or set of scores moves in one direction, the other set of scores moves in the opposite direction. A correlation coefficient of -1.0 would represent a perfect, negative relationship between two variables. A correlation coefficient near 0, however, would indicate a lack of relationship between two variables, or two sets of scores.
Reference
Glass, G.V, and Hopkins, K. D. Statistical Methods in Education and Psychology. Englewood Cliffs, New jersey: Prentice-Hall, Inc, 1984.