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.