Using normal score transformations

Available with Geostatistical Analyst license.

Normal score transformation (NST) changes your data so that it follows a univariate standard normal distribution. This is an important step when you create quantile or probability maps using simple, probability, or disjunctive kriging. Also, simple kriging models that will be used as input to the Gaussian Geostatistical Simulations tool should be based on normally distributed data. The steps below describe how to apply a normal score transformation to the data when using simple kriging.

1. Choose Kriging/CoKriging under Geostatistical Methods on the Geostatistical Wizard method selection window.
2. Click Next.
3. Choose Simple from the list of kriging methods. Transformation type is automatically set to Normal Score.
4. Click Next.
5. Choose the number of bars you want to display in the Density chart by setting the slider in the upper right part of the interface. Click Cumulative to switch the display to a cumulative distribution of the data, or click Normal QQPlot to display the normal quantile-quantile plot of the data after the transformation.
6. Choose Direct, Linear, Gaussian Kernels, or Multiplicative Skewing from the Approximation method list.
   1. If Multiplicative Skewing is chosen, choose a base distribution: Student's t, Lognormal, Gamma, Empirical, or Log Empirical.
7. If you are using cokriging and need to transform the other dataset(s), switch datasets by clicking the Dataset Selection arrow. Define a normal score transformation for the other datasets following steps 5 and 6.
8. Click Next and continue with the other steps in Geostatistical Wizard to create a surface using a normal score transformation on your data.