INTERQUARTILE RANGE

INTERQUARTILE RANGE (LET)

Let Subcommand

Compute the interquartile range for a variable.

The interquartile range is:
IQ = UPPER QUARTILE - LOWER QUARTILE

That is, it is the difference betweeen the 75th and 25th percentiles of a variable.

The interquartile range is used as a robust measure of scale. That is, it is an alternative to the standard deviation. The interquartile range is less effected by extremes than the standard deviation. It is the measure of scale used by the box plot.

LET <par> = INTERQUARTILE RANGE <y>             <SUBSET/EXCEPT/FOR qualification>
where <y> is the response variable;
            <par> is a parameter where the computed interquartile range is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

LET A = INTERQUARTILE RANGE Y1
LET A = INTERQUARTILE RANGE Y1 SUBSET TAG > 2

Support for the interquartile range has been added to the following commands and plots:
IQ RANGE PLOT
CROSS TABULATE IQ RANGE PLOT
BOOTSTRAP IQ RANGE PLOT
JACKNIFE IQ RANGE PLOT
DEX IQ RANGE PLOT
IQ RANGE BLOCK PLOT
INTERACTION IQ RANGE PLOT
IQ RANGE INFLUENCE CURVE


LET Y2 = CROSS TABULATE IQ RANGE X1 X2


SET SCALE STATISTIC IQ RANGE
LET Y2 = STANDARDIZE Y X1 X2

None

IQ RANGE is a synonym for INTERQUARTILE RANGE.

AVERAGE ABSOLUTE DEVIATION	= Compute the average absolute deviation of a variable.
MEDIAN ABSOLUTE DEVIATION	= Compute the median absolute deviation of a variable.
STANDARD DEVIATION	= Compute the standard deviation of a variable.
VARIANCE	= Compute the variance of a variable.
RANGE	= Compute the range of a variable.

Robust Data Analysis

2001/10

LET Y1 = LOGISTIC RANDOM NUMBERS FOR I = 1 1 100
LET A1 = INTERQUARTILE RANGE Y1

SKIP 25
READ GEAR.DAT DIAMETER BATCH
TITLE AUTOMATIC
XLIMITS 1 10
MAJOR XTIC MARK NUMBER 10
MINOR XTIC MARK NUMBER 0
XTIC OFFSET 1 1
X1LABEL BATCH
Y1LABEL INTERQUARTILE RANGE OF DIAMETER
IQ RANGE PLOT DIAMETER BATCH