DIFFERENCE OF RELATIVE VARIANCE

DIFFERENCE OF RELATIVE VARIANCE (LET)

Let Subcommand

Compute the difference between the relative variances for two response variables.

The relative variance is:
\( \mbox{relvar} = \frac{100 s^2}{|\bar{x}|} \)

with s² and \( \bar{x} \) denoting the variance and the mean, respectively.

Some analysts prefer to call this the percent relative variance and the value obtained without multiplying by 100 the relative variance. If this is your preference, simply divide the obtained value by 100 with the LET command.

For the difference of relative variances, the relative variance is computed for each of two samples then their difference is taken.

LET <par> = DIFFERENCE OF RELATIVE VARIANCE <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 relative variances is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

LET A = DIFFERENCE OF RELATIVE VARIANCE Y1 Y2
LET A = DIFFERENCE OF RELATIVE VARIANCE Y1 Y2 SUBSET X > 1

Dataplot statistics can be used in a number of commands. For details, enter
HELP STATISTICS

None

None

RELATIVE VARIANCE	= Compute the relative variance.
RELATIVE SD	= Compute the relative sd.
COEFFICIENT OF VARIATION	= Compute the coefficient of variation.
STANDARD DEVIATION	= Compute the standard deviation.
DIFFERENCE OF RELATIVE SD	= Compute the difference of the relative standard deviations.
DIFFERENCE OF COEFFICIENT OF VARIATION	= Compute the difference of the coefficient of variation.
DIFFERENCE OF SD	= Compute the difference of standard deviations.
STATISTICS PLOT	= Generate a statistic versus subset plot.

Data Analysis

2003/03

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

Dataplot generated the following output.

       *****************************************************
       **  LET A = DIFFERENCE OF RELATIVE VARIANCE Y1 Y2  **
       *****************************************************
  
  
 THE COMPUTED VALUE OF THE CONSTANT A             =  0.55207367E+01
  
  
       ********************************************************
       **  TABULATE DIFFERENCE OF RELATIVE VARIANCE Y1 Y2 X  **
       ********************************************************
  
  
                 *    Y1       AND Y2
     X           *    DIFFERENCE OF RELATIVE VARIANCES
 **********************************************
     1.00000     *    -1.70965
     2.00000     *    0.933569
     3.00000     *     2.64045
  
       GROUP-ID AND STATISTIC WRITTEN TO FILE DPST1F.DAT