Making a Scatter Diagram With Regression Line Using Excel 2007
To demonstrate the procedure, we will make a scatter diagram from Table 1 on page 179
of Michael Sullivan, Fundamentals of Statistics, 3rd edition, Pearson Education, Inc.
2011.
Club-head Speed (mph) Distance (yards)
100
257
102
264
103
274
101
266
105
277
100
263
99
258
105
275
Now open up a blank worksheet in Excel 2007. Enter Club-Head Speed (mph) and the
speeds in column A. Enter Distance (yards) and the distances in column B under
Frequency. The result will look something like:
A
B
Club-head Speed (mph) Distance (yards)
100
252
102
264
103
274
101
266
105
277
100
263
99
258
105
275
Next highlight everything you just entered and click on the Insert tab. Choose Scatter and
then click on the option in the top left, Scatter with only Markers. You will see a graph
like the following.
Next, in the Chart Layouts window, click the down arrow twice and click on the option
on the right, Layout 9. The graph will now look like the following.
You will need to change chart title and the axis titles to something appropriate for your
data. For the this example, I chose Driving Distance vs Club-head Speed as the chart
title, Club-head Speed (mph) for the x-axis title and Distance (yards) for the y-axis
title. After making these changes, the graph should look like the following.
If you click on the chart title, you can reduce the font size. There is no need for the chart
title font to much more than 2 points bigger than the axis title font. In this case the axis
titles use 10 point font, so I decided to use 12 point font for the chart title. The legend box
on the right that shows the symbol used for data points and the line style. This is not very
useful, so delete it. Similarly, the non-numbered horizontal grid lines do not help much. If
you are careful, you can select them with the cursor arrow and then delete them.
The equation shown in the graph is the equation for the regression line. Move the box
containing this equation and R-squared to an empty area of the graph so you can see it
and the graph better. You could also delete the regression equation and R-squared
entirely, but you should write them down before you do. You will need to state the
regression equation and R-squared in your analysis of the scatter diagram, so it is good to
take advantage of what Excel provides for you automatically.
Finally, if you right click on the line through the middle of the chart, a menu will appear.
Click on Format Trendline. In the box labeled Forecast, enter 0.5 next to Forward and
Backward. This will extend the regression line a half unit beyond the points you plotted.
This helps you find the ends of the regression line from among the points you plotted. If
you want to reduce the range of either axis, click on that axis and increase the minimum
or decrease the maximum to an appropriate value. Our current graph is fine in this
respect. The finished scatter diagram will look something like the following.