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LILFOR.DOC
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1987-02-07
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LILFOR
This program does two things. It prints a graph that can be used to hand
plot a sample CDF to perform the Lilliefors test for normality. It also reads
data from disk or keyboard and performs the Lilliefors test, printing both
graphic and numeric output.
To do the test, there must be between 4 and 255 pieces of data. The upper
limit of 255 may be increased by changing the value of "Limit" in the constant
declaration at the beginning of the program. Data in disk files must be in space
delimited ASCII (SDA) format. Variables are in columns. Each case is in a
separate row, with one or more spaces separating each number. All data should be
numeric; no letters. See SAMPLE.SDA for an example.
The Lilliefors test is an attractive alternative to the Chi-Square test
usually used to test for normality. The test is simple to use. If the sample CDF
falls outside the Lilliefors bounds for the selected significance level, the
hypothesis that the data is normally distributed is rejected. Try the program
with a few sample data sets to get the idea. A number of recent statistics books
discuss this test, e.g. Iman and Conover, "A Modern Approach to Statistics",
Wiley; Conover, "Practical Nonparametric Statistics", Wiley; and Milton and
Arnold, "Probability and Statistics in the Engineering and Computing Sciences",
McGraw Hill. Conover gives the table of quantiles originally used in this
program. The quantiles used in version 1.1 come from Dallal and Wilkinson, "An
analytic approximation to the Distribution of Lilliefor's test statistic for
normality" in The November 1986 American Statistician (Vol 40 No 4).
The printer control codes included in the program are for an Epson RX-80
printer. They should also work with other Epson 9 pin dot matrix printers. These
codes do not work with the Star printers I am familiar with, nor do they work
with the Epson LQ series 24 pin printers. All printer codes used are contained
in the procedure DefinePrintVars at the beginning of the program. If you need to
change the codes, this is the only place you have to look. The codes are defined
in global variables as ASCII strings. For example the reset printer code is
given as #27#64, meaning ASCII 27 (ESC) followed by ASCII 64 (@). The maximum
length string permitted is 6 (the reset printer code is a string of length 2).
If you need longer strings, change the length in the VAR declaration just above
the procedure. All this presumes, of course, that you have a Turbo Pascal
compiler available to recompile after the changes. If you exhaust all other
possibilities and still need the changes made, send a disk, a self addressed
stamped return mailer and a thorough description of the required changes to me
and I'll make them for you. Send to Joe Hudson, Dept. of Science and Math, GMI,
1700 W. Third Ave. Flint, MI 48502.
This program was written by Joseph C. Hudson with major contributions in
the non-statistical parts by Joseph Dear. The program is hereby placed in the
public domain, with no guarantees of suitability or accuracy, though we tried
our best. If you use any part of the code in your own work, we would appreciate
acknowledgment.
P.S. If you get stuck in a submenu and want to get out, use the escape key.