I have a shapefile with an attribute field with a range of numerical values.
How do I derive z-score values for this field using ArcGIS for Desktop?
Here are the steps for calculating Z-Scores in ArcGIS, in this case I have included some screen captures of calculating Z-scores for a field named SourceData.
The formula for Z-Scores is SourceData - Mean / Standard Deviation. Here's what it looks like the Formula Calculator (Note the parenthesis around the first part of the formula):
You can check your results by running Statistics on the zscore field. A Z-score will have a mean of zero and a standard deviation of one.