#DESCRIPTIVES
DESCRIPTIVES
/VARIABLES=VAR_LIST
/MISSING={VARIABLE,LISTWISE} {INCLUDE,NOINCLUDE}
/FORMAT={LABELS,NOLABELS} {NOINDEX,INDEX} {LINE,SERIAL}
/SAVE
/STATISTICS={ALL,MEAN,SEMEAN,STDDEV,VARIANCE,KURTOSIS,
SKEWNESS,RANGE,MINIMUM,MAXIMUM,SUM,DEFAULT,
SESKEWNESS,SEKURTOSIS}
/SORT={NONE,MEAN,SEMEAN,STDDEV,VARIANCE,KURTOSIS,SKEWNESS,
RANGE,MINIMUM,MAXIMUM,SUM,SESKEWNESS,SEKURTOSIS,NAME}
{A,D}
The DESCRIPTIVES procedure reads the active dataset and outputs
linear descriptive statistics requested by the user. It can also
compute Z-scores.
The VARIABLES subcommand, which is required, specifies the list of
variables to be analyzed. Keyword VARIABLES is optional.
All other subcommands are optional:
The MISSING subcommand determines the handling of missing variables.
If INCLUDE is set, then user-missing values are included in the
calculations. If NOINCLUDE is set, which is the default,
user-missing values are excluded. If VARIABLE is set, then missing
values are excluded on a variable by variable basis; if LISTWISE is
set, then the entire case is excluded whenever any value in that case
has a system-missing or, if INCLUDE is set, user-missing value.
The FORMAT subcommand has no effect. It is accepted for backward
compatibility.
The SAVE subcommand causes DESCRIPTIVES to calculate Z scores for
all the specified variables. The Z scores are saved to new variables.
Variable names are generated by trying first the original variable
name with Z prepended and truncated to a maximum of 8 characters, then
the names ZSC000 through ZSC999, STDZ00 through STDZ09,
ZZZZ00 through ZZZZ09, ZQZQ00 through ZQZQ09, in that order.
Z-score variable names may also be specified explicitly on VARIABLES
in the variable list by enclosing them in parentheses after each
variable. When Z scores are calculated, PSPP ignores
TEMPORARY, treating
temporary transformations as permanent.
The STATISTICS subcommand specifies the statistics to be displayed:
ALL
All of the statistics below.MEAN
Arithmetic mean.SEMEAN
Standard error of the mean.STDDEV
Standard deviation.VARIANCE
Variance.KURTOSIS
Kurtosis and standard error of the kurtosis.SKEWNESS
Skewness and standard error of the skewness.RANGE
Range.MINIMUM
Minimum value.MAXIMUM
Maximum value.SUM
Sum.DEFAULT
Mean, standard deviation of the mean, minimum, maximum.SEKURTOSIS
Standard error of the kurtosis.SESKEWNESS
Standard error of the skewness.
The SORT subcommand specifies how the statistics should be sorted.
Most of the possible values should be self-explanatory. NAME causes
the statistics to be sorted by name. By default, the statistics are
listed in the order that they are specified on the VARIABLES
subcommand. The A and D settings request an ascending or
descending sort order, respectively.
Example
The physiology.sav file contains various physiological data for a
sample of persons. Running the DESCRIPTIVES command on the
variables height and temperature with the default options allows one
to see simple linear statistics for these two variables. In the
example below, these variables are specfied on the VARIABLES
subcommand and the SAVE option has been used, to request that Z
scores be calculated.
After the command completes, this example runs DESCRIPTIVES again,
this time on the zheight and ztemperature variables, which are the two
normalized (Z-score) variables generated by the first DESCRIPTIVES
command.
get file='physiology.sav'.
descriptives
/variables = height temperature
/save.
descriptives
/variables = zheight ztemperature.
In the output below, we can see that there are 40 valid data for each of the variables and no missing values. The mean average of the height and temperature is 16677.12 and 37.02 respectively. The descriptive statistics for temperature seem reasonable. However there is a very high standard deviation for height and a suspiciously low minimum. This is due to a data entry error in the data.
In the second Descriptive Statistics output, one can see that the mean and standard deviation of both Z score variables is 0 and 1 respectively. All Z score statistics should have these properties since they are normalized versions of the original scores.
Mapping of Variables to Z-scores
┌────────────────────────────────────────────┬────────────┐
│ Source │ Target │
├────────────────────────────────────────────┼────────────┤
│Height in millimeters │Zheight │
│Internal body temperature in degrees Celcius│Ztemperature│
└────────────────────────────────────────────┴────────────┘
Descriptive Statistics
┌──────────────────────────────────────────┬──┬───────┬───────┬───────┬───────┐
│ │ N│ Mean │Std Dev│Minimum│Maximum│
├──────────────────────────────────────────┼──┼───────┼───────┼───────┼───────┤
│Height in millimeters │40│1677.12│ 262.87│ 179│ 1903│
│Internal body temperature in degrees │40│ 37.02│ 1.82│ 32.59│ 39.97│
│Celcius │ │ │ │ │ │
│Valid N (listwise) │40│ │ │ │ │
│Missing N (listwise) │ 0│ │ │ │ │
└──────────────────────────────────────────┴──┴───────┴───────┴───────┴───────┘
Descriptive Statistics
┌─────────────────────────────────────────┬──┬─────────┬──────┬───────┬───────┐
│ │ │ │ Std │ │ │
│ │ N│ Mean │ Dev │Minimum│Maximum│
├─────────────────────────────────────────┼──┼─────────┼──────┼───────┼───────┤
│Z─score of Height in millimeters │40│1.93E─015│ 1.00│ ─5.70│ .86│
│Z─score of Internal body temperature in │40│1.37E─015│ 1.00│ ─2.44│ 1.62│
│degrees Celcius │ │ │ │ │ │
│Valid N (listwise) │40│ │ │ │ │
│Missing N (listwise) │ 0│ │ │ │ │
└─────────────────────────────────────────┴──┴─────────┴──────┴───────┴───────┘