Dataplot Vol 2 Vol 1

DIFFERENCE OF INTERQUARTILE RANGE

Name:
DIFFERENCE OF INTERQUARTILE RANGE (LET)
Type:
Let Subcommand
Purpose:
Compute the difference between the interquartile ranges for two response variables.
Description:
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 normalized interquartile range is

NIQ = 0.7413*IQ

This normalization is based on the fact that for a normal distribution, the interquartile range is approximately 1.349 times the standard deviation.

For the differeence of interquartile ranges, the interquartile range is computed for each of two samples then their difference is taken.

Syntax 1:
LET <par> = DIFFERENCE OF INTERQUARTILE RANGE <y1> <y2>
<SUBSET/EXCEPT/FOR qualification>
where <y1> is the first response variable;
<y2> is the first response variable;
<par> is a parameter where the computed difference of the interquartile ranges is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Syntax 2:
LET <par> = DIFFERENCE OF NORMALIZED INTERQUARTILE RANGE <y1> <y2>
<SUBSET/EXCEPT/FOR qualification>
where <y1> is the first response variable;
<y2> is the first response variable;
<par> is a parameter where the computed difference of the normalized interquartile ranges is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.
Examples:
LET A = DIFFERENCE OF INTERQUARTILE RANGE Y1 Y2
LET A = DIFFERENCE OF INTERQUARTILE RANGE Y1 Y2 SUBSET X > 1
LET A = DIFFERENCE OF NORMALIZED INTERQUARTILE RANGE Y1 Y2
Note:
Dataplot statistics can be used in a number of commands. For details, enter

Default:
None
Synonyms:
IQ RANGE is a synonym for INTERQUARTILE RANGE
IQR is a synonym for INTERQUARTILE RANGE
SCALED is a synonym for NORMALIZED
The word OF is optional
Related Commands:
 INTERQUARTILE RANGE = Compute the interquartile range. RANGE = Compute the range. MIDRANGE = Compute the midrange. PERCENTILE = Compute a percentile. QUANTILE = Compute a quantile. STANDARD DEVIATION = Compute the standard deviation. DIFFERENCE OF RANGE = Compute the difference of the range. DIFFERENCE OF MIDRANGE = Compute the difference of the midrange. DIFFERENCE OF SD = Compute the difference of standard deviations. DIFFERENCE OF QUANTILE = Compute the difference of a quantile. STATISTICS PLOT = Generate a statistic versus subset plot. BOOTSTRAP PLOT = Generate a bootstrap plot. TABULATE = Perform a tabulation for a specified statistic.
Applications:
Data Analysis
Implementation Date:
2003/03
Program:
```SKIP 25
READ IRIS.DAT Y1 TO Y4 X
.
LET A = DIFFERENCE OF INTERQUARTILE RANGE Y1 Y2
TABULATE DIFFERENCE OF INTERQUARTILE RANGE Y1 Y2 X
.
XTIC OFFSET 0.2 0.2
X1LABEL GROUP ID
Y1LABEL DIFFERENCE OF IQ RANGES
CHAR X
LINE BLANK
DIFFERENCE OF INTERQUARTILE RANGE PLOT Y1 Y2 X
CHAR X ALL
LINE BLANK ALL
BOOTSTRAP DIFFERENCE OF INTERQUARTILE RANGE PLOT Y1 Y2 X
```
Dataplot generated the following output.
```       ********************************************
**  LET A = DIFFERENCE OF IQ RANGE Y1 Y2  **
********************************************

THE COMPUTED VALUE OF THE CONSTANT A             =  0.72499990E+00

***********************************************
**  TABULATE DIFFERENCE OF IQ RANGE Y1 Y2 X  **
***********************************************

*    Y1       AND Y2
X           *    DIFFERENCE OF INTERQUARTILE RA
**********************************************
1.00000     *   -0.175001
2.00000     *    0.200000
3.00000     *    0.450000

GROUP-ID AND STATISTIC WRITTEN TO FILE DPST1F.DAT
```

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Date created: 03/27/2003
Last updated: 11/09/2015