1. Scatter Diagram Method:
This is a simple method to find the nature or type (positive or negative) of correlation showing the values of variable X on X-axis and that of variable Y on Y-axis by an appropriate scale, the points corresponding to n ordered pairs (x1, y1), (x2, y2), …. (xn, yn) are plotted on the graph paper. The graph showing the plotted points is called a scatter diagram. The pattern of points on a scatter diagram shows the nature or type of correlation and the strength of correlation up to some extent.
2. Karl Pearson’s Product Moment Method:
The method of finding the measure of the strength of linear correlation between two variables X and Y using the n pairs (x1, y1), (x2, y2), …….. (xn, yn) of observations on two variables X and Y is called Karl Pearson’s product moment method.
3. Spearman’s Rank Correlation Method:
When n pairs of observations (x1, y1), (x2, y2), …, (xn, yn) on two variables X and Y are given, then the method by which the correlation coefficient computed using the ranks assigned to the values of two variables in descending order of magnitudes is called Spearman’s rank correlation method.
