The simplest device for studding correlation in two variables is a special type of dot chart called Dotogram or scatter diagram. When this method is used, the given data are plotted on a graph paper in the form of dots, for each pair of X and Y values we put dots and thus obtain as many points as the number of observations. By looking to the scatter of the various points, we can form an idea as to whether the variables are related or not. The more the plotted points “scatter” over a chart the lesser is the degree of relationship in between the two variables.