Microsoft Excel:Microsoft Excel:Line of Best FitLine of Best Fit

Tim CourtneyTim CourtneyAileen RichardsAileen Richards

Joshua TunziJoshua TunziDewey WardDewey Ward

Open the Trendline MenuOpen the Trendline Menu

Step 1 – Step 1 – Right-click Right-click on a data on a data point.point.

Step 2 – Left-Step 2 – Left-click “Add click “Add Trendline”.Trendline”.

Select a TrendlineSelect a Trendline

Step 3 – Left-Step 3 – Left-click on the click on the Regression Regression Type that Type that appears to appears to match your match your data best.data best.

Analyze TrendAnalyze Trend

Step 4 – Click the Step 4 – Click the “Options” Tab.“Options” Tab.

Step 5 – Mark Step 5 – Mark check boxes as check boxes as shown.shown.

Step 6 – Click Step 6 – Click “Ok”.“Ok”.

Interpreting the TrendlineInterpreting the Trendline

Step 7 – RStep 7 – R22 is is the quality of the quality of fit. Repeat fit. Repeat steps 1 steps 1 through 6 with through 6 with other other regression regression types to find types to find the best fit.the best fit.

Trendline UseTrendline Use

An RAn R22 of 1 fits the data perfectly. of 1 fits the data perfectly.• This is unlikely to happen with real data.This is unlikely to happen with real data.

Beware of “overfitting” a curve with Beware of “overfitting” a curve with a high order polynomial.a high order polynomial.

Equation of trendline can be used to Equation of trendline can be used to predict results of future data.predict results of future data.

ConclusionConclusion

Trendlines are a powerful tool in Trendlines are a powerful tool in explaining experimental phenomena explaining experimental phenomena and predicting future results.and predicting future results.

Excel can quickly and easily find Excel can quickly and easily find common trendlines.common trendlines.

For more difficult trends, students For more difficult trends, students may look into non-linear least may look into non-linear least squares regression with a program squares regression with a program such as MATLAB.such as MATLAB.