
DIFFERENCE OF SNName:
That is, for each i we compute the median of {x_{i}  x_{j} j = 1, ..., n}. The median of these n numbers is then the estimate of S_{n}. The constant c is determined to make S_{n} a consistent estimator. The value used is 1.1926 (this is the value needed to make S_{n} a consistent estimator for data from a normal distribution). The S_{n} statistic measures typical distances between values (in contrast to the median absolute deviation and the standard deviation which measure the distance from a central location). Enter HELP SN SCALE for a more detailed discussion of the S_{n} scale estimate. For the difference of S_{n} scale estimates, the S_{n} scale estimate is computed for each of the two samples then their difference is taken.
<SUBSET/EXCEPT/FOR qualification> where <y> is the response variable; <par> is a parameter where the computed difference of S_{n} scale statistics is stored; and where the <SUBSET/EXCEPT/FOR qualification> is optional.
LET A = DIFFERENCE OF SN Y1 Y2 SUBSET TAG > 2
Mosteller and Tukey (1977), "Data Analysis and Regression: A Second Course in Statistics," AddisonWesley, pp. 203209.
SKIP 25 READ IRIS.DAT Y1 TO Y4 X . LET A = DIFFERENCE OF SN Y1 Y2 TABULATE DIFFERENCE OF SN Y1 Y2 X . XTIC OFFSET 0.2 0.2 MAJOR XTIC MARK NUMBER 3 MINOR XTIC MARK NUMBER 0 X1LABEL GROUP ID Y1LABEL DIFFERENCE OF SN CHARACTER X LINE BLANK DIFFERENCE OF SN PLOT Y1 Y2 X CHARACTER X ALL LINE BLANK ALL BOOTSTRAP DIFFERENCE OF SN PLOT Y1 Y2 XDataplot generated the following output. ************************************** ** LET A = DIFFERENCE OF SN Y1 Y2 ** ************************************** THE COMPUTED VALUE OF THE CONSTANT A = 0.47704038E+00 ***************************************** ** TABULATE DIFFERENCE OF SN Y1 Y2 X ** ***************************************** * Y1 AND Y2 X * DIFFERENCE OF SN ********************************************** 1.00000 * 0.298023E06 2.00000 * 0.238520 3.00000 * 0.357780
 
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Date created: 05/21/2003 