Include Top

How Do I Perform a Box-Cox Transformation in Excel Using SigmaXL?

Box-Cox Transformation

This is a standalone tool that allows you to visually see how the Box-Cox transformation selects a rounded or optimal lambda value.

  1. Open the file Nonnormal Cycle Time2.xlsx. Select Sheet 1 Tab.
  2. Click SigmaXL > Process Capability > Nonnormal > Box-Cox Transformation (or SigmaXL > Data Manipulation > Box-Cox Transformation or SigmaXL > Control Charts > Nonnormal > Box-Cox Transformation). Ensure that the entire data table is selected. If not, check Use Entire Data Table. Click Next.
  3. Select Cycle Time (Minutes), click Numeric Data Variable (Y) >>. The selected variable must contain all positive values.

  4. Box-Cox Transformation

Tip: Note that while this tool is often successful to transform the data to normality, there may not be a suitable transformation to make the data normal. The output report indicates the Anderson-Darling p-value for the transformed data. You may wish to check Do not store if transformed data is not normal. Another option is Do not store transformed data if Lambda = 1 falls within 95% CI. This latter option prevents you from using transformations that do not result in a statistically significant improvement towards normality.

  1. Click OK. The resulting report is shown:
  2. Box-Cox Transformation

  3. The fact that Lambda=1 falls outside of the 95% confidence interval tells us that the transformation is statistically significant. The Anderson-Darling p-value of 0.4041 indicates that we cannot reject the null hypothesis that the transformed data is normal, so the Ln transformation has successfully converted the data to normality.

Define, Measure, Analyze, Improve, Control

Lean Six Sigma Software Excel Add-in

Simulate, Optimize,

Lean Six Sigma Software Excel Add-in

Web Demos

Our CTO and Co-Founder, John Noguera, regularly hosts free Web Demos featuring SigmaXL and DiscoverSim
Click here to view some now!

Contact Us

Phone: 1.888.SigmaXL (744.6295)