SPSS® 12.0 Command Syntax Reference

Z Scores
DESCRIPTIVES 463
The z-score transformation standardizes variables to the same scale, producing new variables
with a mean of 0 and a standard deviation of 1. These variables are added to the working data
file.
• To obtain z scores for all specified variables, use the SAVE subcommand.
• To obtain z scores for a subset of variables, name the new variable in parentheses following
the source variable on the VARIABLES subcommand and do not use the SAVE subcommand.
• Specify new names individually; a list in parentheses is not recognized.
• The new variable name can be any acceptable variable name that is not already part of the
working data file. For information on variable naming rules, see “Variable Names” on p.
21.
Example
DESCRIPTIVES VARIABLES=NTCSAL NTCPUR (PURCHZ) NTCPRI (PRICEZ).
• DESCRIPTIVES creates z-score variables named PURCHZ and PRICEZ for NTCPUR and
NTCPRI, respectively. No z-score variable is created for NTCSAL.
SAVE Subcommand
SAVE creates a z-score variable for each variable specified on the VARIABLES subcommand.
The new variables are added to the working data file.
• When DESCRIPTIVES creates new z-score variables, it displays the source variable
names, the new variable names, and their labels in the Notes table.
• DESCRIPTIVES automatically supplies variable names for the new variables. The new
variable name is created by prefixing the letter Z to the first seven characters of the source
variable name. For example, ZNTCPRI is the z-score variable for NTCPRI.
• If the default naming convention duplicates variable names in the working data file,
DESCRIPTIVES uses an alternative naming convention: first ZSC001 through ZSC099,
then STDZ01 through STDZ09, then ZZZZ01 through ZZZZ09, and then ZQZQ01 through
ZQZQ09.
• Variable labels are created by prefixing ZSCORE to the first 31 characters of the source
variable label. If the alternative naming convention is used, DESCRIPTIVES prefixes
ZSCORE(varname) to the first 31 characters of the label. If the source variable does not
have a label, DESCRIPTIVES uses ZSCORE(varname) for the label.
• If you specify new names on the VARIABLES subcommand and use the SAVE subcommand,
DESCRIPTIVES creates one new variable for each variable on the VARIABLES subcommand,
using default names for variables not assigned names on VARIABLES.
• If at any time you want to change any of the variable names, whether those DESCRIPTIVES
created or those you previously assigned, you can do so with the RENAME VARIABLES
command.