Use finite differences to identify the degree of the polynomial that best describes the data.

Connect the two centers to produce the trend line

Step-by-step explanation:

When the dots have been plotted, there are three steps to find the trend line on a scatter plot:

1.  Draw a vertical line that separates the full set of points into two sets, each with the same number of dots.

2.Mark with a special sign (e.g + or ×) the middle value in each of the two sets obtained in the previous step.

3.Join the two marks mentioned in the step (2) with a straight line, and extend it to the edges of the graph. This line is the trend line, and this is the last step.

Thus, the last step when using the divide-center method to find the line on scatter plot is Connect the two centers to produce the trend line.