In SPSS, what is the difference between system-missing and user-missing values?
In SPSS, observations with system-missing or user-missing values are excluded from data manipulation and analyses.
The program by default assigns system-missing values, while users
define user-missing values. System-missing values are represented as
a . (period) in the data view. User-missing
values are actual scores that are meant to signify a missing
observation.
Suppose you want to ignore a particular value or a range of values
in variable x and y when conducting an
analysis. You can use the MISSING VALUES command to set
these values as user-missing:
Once the command is executed, the value 5 in the variable
x, and 6 through 10 in the variable y, are
considered missing. When computing descriptive statistics,
observations with these values are excluded. However, these values
physically remain unchanged; you will not observe any change in the
data view.
Another difference is that user-missing values are ignored in the
SYSMIS() function, which only detects system-missing
observations. If you set some values as system-missing rather than
user-missing, use the RECODE commmand with
SYSMIS, for example:
Note that the INTO subcommand generates a new variable
to store recoded values.
Last modified on May 10, 2011.
