DIFFERENCE OF VARIANCE OF THE MEAN

DIFFERENCE OF VARIANCE OF THE MEAN (LET)

Let Subcommand

Compute the difference between the variance of the means for two response variables.

The variance of the mean is:
\( s_{mean}^2 = \frac{s^2}{n} \)

with s² and n denoting the variance and the number of observations, respectively.

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

LET <par> = DIFFERENCE OF VARIANCE OF THE MEAN <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 variance of the means is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

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

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

None

None

SD OF THE MEAN	= Compute the standard deviaiton of the mean.
VARIANCE	= Compute the variance.
STANDARD DEVIATION	= Compute the standard deviation.
MEAN	= Compute the mean.
DIFFERENCE OF MEAN	= Compute the difference of the means.
DIFFERENCE OF VARIANCE	= Compute the difference of variances.
DIFFERENCE OF SD OF THE MEAN	= Compute the difference of the standard deviation of the mean.
STATISTICS PLOT	= Generate a statistic versus subset plot.
BOOTSTRAP PLOT	= Generate a bootstrap plot.
TABULATE	= Perform a tabulation for a specified statistic.

Data Analysis

2003/03

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

Dataplot generated the following output.

       ********************************************************
       **  LET A = DIFFERENCE OF VARIANCE OF THE MEAN Y1 Y2  **
       ********************************************************
  
  
 THE COMPUTED VALUE OF THE CONSTANT A             =  0.33047604E-02
  
  
       ***********************************************************
       **  TABULATE DIFFERENCE OF VARIANCE OF THE MEAN Y1 Y2 X  **
       ***********************************************************
  
  
                 *    Y1       AND Y2
     X           *    DIFFERENCE OF VARIANCE OF THE MEANS
 **********************************************
     1.00000     *   -0.388816E-03
     2.00000     *    0.335927E-02
     3.00000     *    0.600677E-02
  
       GROUP-ID AND STATISTIC WRITTEN TO FILE DPST1F.DAT