Explainations: Add a Trendline

Step 1

To make a trendline, or regression, that fits your data, first right click on the line connecting your data points and select "Add Trendline."

Step 2

In the dialog box, under "Trend/Regression type" select Linear, because we want an equation that represents our data as a straight line.

Step 3

Then, select the Options tab to set some trendline options.

Step 4

Mark the bottom two checkboxes labeled "Display equation on chart" and "Display R-squared value on chart". Leave all of the other options as is. Click OK to finish.

Step 5

The trendline you added is the black line on the chart. If the trendline is a good representation of your data, then the R-squared value will be close to -1 or 1, if it is a very bad representation, then it will be close to zero

Step 6

Remember, all lines can be expressed as y=mx+b, where 'm' is the slope and 'b' is the y-intercept. Find the number corresponding to the slope in your trendline equation. Put this number in the blue cell with the label "slope of trend line", cell D9. Now find the number corresponding to the y-intercept and put it in the blue cell labeled "y-intercept of trend line", cell D10.