SPSS® 12.0 Command Syntax Reference

• The method keywords follow the specifications for break points.
EXAMINE 523
For each of the following methods of percentile calculation, w is the sum of the weights for
all nonmissing cases, p is the specified percentile divided by 100, and X i is the value of the
ith case (cases are assumed to be ranked in ascending order). For details on the specific
formulas used, see the SPSS Statistical Algorithms chapter for EXAMINE.
HAVERAGE Weighted average at ( + )p.
The percentile value is the weighted average
of Xi and Xi + 1 , where i is the integer part of ( w + 1)p.
This is the default
if PERCENTILES is specified without a keyword.
WAVERAGE Weighted average at . The percentile value is the weighted average of
and , where i is the integer part of wp.
ROUND Observation closest to wp. The percentile value is Xi or Xi + 1 , depending
upon whether i or i+1 is “closer” to wp .
EMPIRICAL Empirical distribution function. The percentile value is Xi , where i is equal
to wp rounded up to the next integer.
AEMPIRICAL Empirical distribution with averaging. This is equivalent to EMPIRICAL, except
when i=wp, in which case the percentile value is the average of Xi and
.
NONE Suppress percentile output. This is the default if PERCENTILES is omitted.
Example
EXAMINE VARIABLE=SALARY /PERCENTILES(10,50,90)=EMPIRICAL.
• PERCENTILES produces the 10th, 50th, and 90th percentiles for the dependent variable
SALARY using the EMPIRICAL distribution function.
PLOT Subcommand
Xi +
1
X( i + 1)
X w 1
Xwp X i
PLOT controls plot output. The default is a vertical boxplot and a stem-and-leaf plot for each
dependent variable for each cell in the model.
• Spread-versus-level plots can be produced only if there is at least one factor variable on
the VARIABLES subcommand. If you request a spread-versus-level plot and there are no
factor variables, the program issues a warning and no spread-versus-level plot is produced.
• If you specify the PLOT subcommand, only those plots explicitly requested are produced.
BOXPLOT Vertical boxplot. The boundaries of the box are Tukey’s hinges. The
median is identified by an asterisk. The length of the box is the interquartile
range (IQR) computed from Tukey’s hinges. Values more than
three IQR’s from the end of a box are labeled as extreme (E). Values
more than 1.5 IQR’s but less than 3 IQR’s from the end of the box are
labeled as outliers (O).
STEMLEAF Stem-and-leaf plot. In a stem-and-leaf plot, each observed value is divided
into two components—leading digits (stem) and trailing digits
(leaf).