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STURANGE.DOC
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1988-07-24
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STUDENTIZED RANGE TEST
AIM: The program is designed to calculate a number which represents the
least amount that any two means can be separated for significance at the 5%
level.
EXAMPLE: The progress of wound healing was compared when 5 different
postoperative regimens were employed after abdominal surgery. The 30
patients in the study were randomly assigned. The numbers below represent
coded data on the duration of healing.
POSTOPERATIVE REGIMEN Test data for Studentized Range
A B C D E 5 6
3 4 2 6 8
3 4 2 6 8 5 7 3 3 2
5 7 3 3 2 5 6 4 5 4
5 6 4 5 4 2 6 3 5 5
2 6 3 5 5 4 9 3 2 6
4 9 3 2 6 5 7 5 4 6
5 7 5 4 6
The table on the right shows the way the data should be entered in a NON-
DOCUMENT mode in a WordStar file, if you wish to enter the data from a file
rather than from the keyboard. Line 1 is the title (65 characters of any
kind); line 2 contains the number of columns, followed by the number of
rows. Thereafter, the data itself is entered, just as in the table on the
left.
Data entry from the keyboard consists of a title (65 characters of any
kind) to identify the data, followed by entry of the raw data (in this
case, the 30 numbers shown above). The program calculates the totals for
each group (column), the means, the means squared and other items in the
Analysis of Variance. The program then selects a number from its built-in
Studentized Range table (4.17 in this example), based upon the number of
groups and the degrees of freedom. It uses this extracted number to
calculate the smallest significant range at the 5% level (2.604 in this
example). All this is printed out along with the raw data.
The program also rearranges the group means in descending order of
magnitude for easy inspection of possible significant differences. In the
ranked example output from the data above, the first mean (Group 2, 6.5)
does not differ from the second (Group 5, 5.167) by at least 2.6, so these
two are not different at the 5% level. The same is true for the second
(Group 5) and third (Group 4) means, and so on. On the other hand, the
first (Group 2) and the last (Group 3) differ by 3.167, which is more than
2.6. Therefore, these two groups are significantly different, and this
fact is printed out.
The user may select just screen output, or screen and printer output.
Printer output is preferred because if there are more than 8 groups, there
is not enough room on the standard 80 column screen to display the columns
without wrap around. If the printer option is selected, columns are
automatically printed in condensed typestyle (SG-10 and similar printers),
which permits all data to fit on the paper without wrap around. Note that
all groups (Columns) must have the same number of data points.
REFERENCE: Goldstein, A. 1964 Biostatistics: An Introductory Text.
Macmillan Company, New York. Pages 71-72 and Table 8.
BASIC VERSION: Dr. Stanley Kaplan May 84
PASCAL VERSION: Dr. Stanley Kaplan Sep 85
UPDATES: Oct 86 (Version 2.00)
Feb 87 (Version 2.10)
Feb 88 (MS-DOS, Version 2.2)