The coefficient of correlation is a measure of the extent to which the movements of two variables are related to each other. A score of -1 indicates perfectly negative correlation, while a score of +1 indicates perfectly positive correlation. The level of correlation is considered to be weak as the coefficient approaches -1, and it is considered to be strong as it approaches +1. Even when there is a high level of correlation, it does not necessarily indicate that there is a significant cause-and-effect relationship. The concept is used in regression analysis.