Specify a Box-Cox transformation for Individual Distribution Identification

Use the Box-Cox transformation to transform your data to follow a normal distribution and to store the transformed data for further analysis. You can use the Box-Cox transformation only with positive data. If your data include negative values or 0, use the Johnson transformation.

Box-Cox power transformation (W = Y^λ)

Select the lambda (λ) value that Minitab uses to transform the data.

• Use optimal λ: Use the optimal lambda, which should produce the best fitting transformation. Minitab rounds the optimal lambda to 0.5 or the nearest integer.

  Note

  To use an exact value instead of a rounded value for optimal λ, choose File > Options > Control Charts and Quality Tools > Other and deselect Use rounded values for Box-Cox transformations when possible.

• λ = 0 (ln): Use the natural log of your data.
• λ = 0.5 (square root): Use the square root of your data.
• Other (enter a value between -5 and 5): Use a specified value for lambda. Other common transformations are square (λ = 2), inverse square root (λ = −0.5), and inverse (λ = −1). In most cases, you should not use a value outside the range of −2 and 2.

Store transformed data in

Single column

Enter a single column of the worksheet to store the transformed values in.

Subgroups across rows of

If you have subgroups arranged in rows across several columns, enter the columns in the worksheet to store the transformed values in.