The main result of a statistical correlation, abbreviated as “r“. The correlation coefficient r denotes the strength of a relationship between two variables; it ranges from -1.0 to +1.0. The closer r is to +1 or -1, the more strongly the two variables are related. If r is positive, the relationship between the variables is also positive (as one variable increases, the other does too). If r is negative, an increase in one variable implies a decrease in the other. If r is close to 0, there is little or no relationship between the variables.
Example: A researcher hypothesizes that taller people have higher self-esteem. After analyzing his data and coming up with an r-value of .08, he abandons his hypothesis because the two variables do not appear to be strongly related at all.
Grinnell, R. (2008). Correlation Coefficient. Psych Central. Retrieved on April 25, 2015, from http://psychcentral.com/encyclopedia/2008/correlation-coefficient/