How are lines of best fit and other trend lines used with scatter plots?

Answer 1

If you are talking about Excel, trend lines are added to the scatter plot chart. Simply left click on a point in the scatter plot and then right click and then click "Add Trendline" in the pop up menu. In the "Format Trendline" pop up, you will see multiple regression/trend types such as exponential, linear, logarithmic, polynomial, power, etc. You can try different types till you get a good fit. Another helpful option in this pop up is the "Display Equation on the Chart" and "Display R-squared value on the chart". The equation gives the ability to calculate any Y-value (dependent variable) if you know the X-value "independent variable". The R² allows you to determine the goodness of fit for each model/type.

Hope this helps