What is the correlation coefficient?
Correlation coefficient (r) is a measure of how strong a linear relationship is between two variables. It is always a number between -1 and +1. A value of -1 or +1 indicates a perfectly linear relationship. The +/- only indicates the direction of the slope of the line. A line with a correlation coefficient of +1.0 will be a perfectly straight line sloping upward and to the right. A line with a correlation coefficient of -1.0 will be a perfectly straight line sloping downward and to the right. The closer the correlation coefficient is to 1.0 (or -1.0 for a negatively sloping line), the better the correlation between the two variables. A coefficient of 0 means there is no relationship between the two variables. Take a look at this correlation coefficient applet to see graph examples for different correlation coefficients. How is the correlation coefficient determined? The correlation coefficient can be calculated manually but it is a very involved and tedious process. It involves knowled
