DIFFERENCE OF SD

DIFFERENCE OF SD (LET)

Let Subcommand

Compute the difference between the standard deviations for two response variables.

The standard deviation is a common measure of the spread of a distribution or variable. The formula is:
For the difference of standard deviations, the standard deviation is computed for each of two samples then their difference is taken.

LET <par> = DIFFERENCE OF SD <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 standard deviations is stored;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

LET A = DIFFERENCE OF SD Y1 Y2
LET A = DIFFERENCE OF SD Y1 Y2 SUBSET X > 1

The difference of standard deviations statistic is also supported for the following commands:
DIFFERENCE OF SD PLOT Y1 Y2 X
CROSS TABULATE DIFFERENCE OF SD PLOT Y1 Y2 X
BOOTSTRAP DIFFERENCE OF SD PLOT Y1 Y2
TABULATE DIFFERENCE OF SD Y1 Y2 X
CROSS TABULATE DIFFERENCE OF SD Y1 Y2 X
LET Z = CROSS TABULATE DIFFERENCE OF SD 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

STANDARD DEVIATION	= Compute the standard deviation.
MEAN	= Compute the meand.
DIFFERENCE OF MEAN	= Compute the difference of the means.
DIFFERENCE OF MAD	= Compute the difference of the mad.
DIFFERENCE OF AAD	= Compute the difference of the aad.
DIFFERENCE OF IQ RANGE	= Compute the difference of the interquartile range.
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 SD Y1 Y2 
TABULATE DIFFERENCE OF SD Y1 Y2 X 
. 
XTIC OFFSET 0.2 0.2 
X1LABEL GROUP ID 
Y1LABEL DIFFERENCE OF SD 
CHAR X 
LINE BLANK 
DIFFERENCE OF SD PLOT Y1 Y2 X 
CHAR X ALL 
LINE BLANK ALL 
BOOTSTRAP DIFFERENCE OF SD PLOT Y1 Y2 X  
    

Dataplot generated the following output.

       **************************************
       **  LET A = DIFFERENCE OF SD Y1 Y2  **
       **************************************
  
  
 THE COMPUTED VALUE OF THE CONSTANT A             =  0.39219981E+00
  
  
       *****************************************
       **  TABULATE DIFFERENCE OF SD Y1 Y2 X  **
       *****************************************
  
  
                 *    Y1       AND Y2
     X           *    DIFFERENCE OF STANDARD DEVIATI
 **********************************************
     1.00000     *   -0.265747E-01
     2.00000     *    0.202373
     3.00000     *    0.313383
  
       GROUP-ID AND STATISTIC WRITTEN TO FILE DPST1F.DAT