ABSTRACT
We now take up a useful method of analyzing the relationship between two variables. We make simultaneous observations on the two variables x and y, say, x1 and y1, then later on another pair x2 and y2, and so on to xn, and yn. Each such pair is at the same time or place, or on the same material. Then we seek to study the relationship between the two variables. For example, can we estimate or predict y from x? Are they closely related, loosely related, or unrelated? One very simple way to gain some insight into the relation is to make a ‘‘scatter diagram’’ that is, to plot each pair of x and y on a graph. Thus with a horizontal x-axis and a vertical y-axis, we first plot y1 against x1 then y2 against x2, and so on. Then a relationship may or may not emerge. Sometimes such a scatter diagram is all that we need in a study.
