Transform nonnormal data

You can transform your data using many functions such as square root, logarithm, power, reciprocal or arcsine.

  • To apply these transformations directly to your data in the worksheet, use the Minitab Calculator.
  • To perform a Box-Cox transformation, choose Stat > Control Charts > Box-Cox Transformation.

    Minitab determines an optimal power transformation. The Box-Cox transformation is easy to understand, but is limited and often does not determine a suitable transformation. It is also only available for data that are positive.

  • To perform a Johnson transformation, choose Stat > Quality Tools > Johnson Transformation.

    If the Box-Cox algorithm does not determine a suitable transformation, then try the Johnson transformation. The Johnson transformation function is more complicated, but is very powerful for determining an appropriate transformation.