The two regression lines indicate the nature and extent of correlation between the variables. The two regression lines can be represented as

Figure Regression Lines and Coefficient of Correlation

In case of perfect positive correlation (r = +1) and in case of perfect negative correlation (r = -1), q = 0, so the two regression lines will coincide, e. we have only one line, see (a) and (b) in Figure.

The farther the two regression lines from each other, lesser will be the degree of correlation and nearer the two regression lines, more will be the degree of correlation, see (c) and (d) in Figure.

If the variables are independent e. r = 0, the lines of regression will cut each other at right angle.

Note : Both the regression lines cut each other at mean value of X and mean value of Y i.e. at X and Y .