Hello, friend. Remember that, for standardizing data, you assume that this data is in a normal distribution. If the data is not in a normal distribution, it is advisable to use percentile rank instead of normalization. A good explanation about the theory and about how to do it in SPSS are in these links: http://www.psychstat.missouristate.edu/introbook/sbk14m.htm http://blogs.perficient.com/businessintelligence/2012/03/21/ranking-your-cases-ibm-spss-statistics/ Anyway, if you are using ArcGIS, a good option is to stretch your raster using "Equalize Histogram", than export the raster ("Data" -> "Export data") using the option "use renderer" and setting the "No Data Value" to 0. This will give you a percentile rank from 1 to 255 and you can re-scale it dividing your raster values by 2.5. Have fun!
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