DIFFERENCE OF BIWEIGHT MIDVARIANCE

DIFFERENCE OF BIWEIGHT MIDVARIANCE (LET)

Let Subcommand

Compute the difference between the biweight midvariances for two response variables.

The biweight midvariance estimate is defined as:

where the summation is restricted to and

and

where MAD is the median absolute deviation.

For the differeence of biweight midvariances, the biweight midvariance is computed for each of two samples then their difference is taken.

LET <par> = DIFFERENCE OF BIWEIGHT MIDVARIANCE <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 biweight midvariances is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

LET A = DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2
LET A = DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 SUBSET X > 1

The difference of biweight midvariances statistic is also supported for the following commands:
DIFFERENCE OF BIWEIGHT MIDVARIANCE PLOT Y1 Y2 X
CROSS TABULATE DIFFERENCE OF BIWEIGHT MIDVARIANCE PLOT Y1 Y2 X
BOOTSTRAP DIFFERENCE OF BIWEIGHT MIDVARIANCE PLOT Y1 Y2
TABULATE DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 X
CROSS TABULATE DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 X
LET Z = CROSS TABULATE DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 X1 X2


Enter

HELP STATISTIC PLOT
HELP CROSS TABULATE PLOT
HELP BOOTSTRAP PLOT
HELP TABULATE
HELP CROSS TABULATE
HELP CROSS TABULATE (LET)


for more information on these plots and commands.

None

None

BIWEIGHT MIDVARIANCE	= Compute the biweight midvariance.
MAD	= Compute the median absolute deviation.
AAD	= Compute the average absolute deviation.
PERCENTAGE BEND MIDVARIANCE	= Compute the percentage bend midvariance.
STANDARD DEVIATION	= Compute the standard deviation.
DIFFERENCE OF AAD	= Compute the difference of average absolute deviations.
DIFFERENCE OF SD	= Compute the difference of standard deviations.
DIFFERENCE OF BIWEIGHT SCALE	= Compute the difference of biweight scales.
STATISTICS PLOT	= Generate a statistic versus subset plot.
CROSS TABULATE PLOT	= Generate a statistic versus two subsets plot.
BOOTSTRAP PLOT	= Generate a bootstrap plot.
TABULATE	= Perform a tabulation for a specified statistic.
CROSS TABULATE	= Perform a cross tabulation for a specified statistic.

Data Analysis

3/2003

SKIP 25 
READ IRIS.DAT Y1 TO Y4 X 
. 
LET A = DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 
TABULATE DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 X 
. 
XTIC OFFSET 0.2 0.2 
X1LABEL GROUP ID 
Y1LABEL DIFFERENCE OF BIWEIGHT MIDVARIANCE 
CHAR X 
LINE BLANK 
DIFFERENCE OF BIWEIGHT MIDVARIANCE PLOT Y1 Y2 X 
CHAR X ALL 
LINE BLANK ALL 
BOOTSTRAP DIFFERENCE OF BIWEIGHT MIDVARIANCE PLOT Y1 Y2 X  
    

Dataplot generated the following output.

       ********************************************************
       **  LET A = DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2  **
       ********************************************************
  
  
 THE COMPUTED VALUE OF THE CONSTANT A             =  0.52265614E+00
  
  
       ***********************************************************
       **  TABULATE DIFFERENCE OF BIWEIGHT MIDVARIANCE Y1 Y2 X  **
       ***********************************************************
  
  
                 *    Y1       AND Y2
     X           *    DIFFERENCE OF BIWEIGHT MIDVARI
 **********************************************
     1.00000     *   -0.349338E-02
     2.00000     *    0.178072
     3.00000     *    0.310287
  
       GROUP-ID AND STATISTIC WRITTEN TO FILE DPST1F.DAT