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FULL-SCREEN MENU-DRIVEN SAMPLE SIZE PROGRAMS USING SAS/AF® SOFTWARE!
L. A. Johnson, IBM Systems Technology Division
P. J. Cirulli, IBM Systems Technology Division
J. A. Bebar, IBM Systems Technology Division
ABSTRACT
This paper describes the efforts and results of
writing a ful1®screen menu®driven application
using base SAS and SAS/AF software. The
application involves making the calculation of
sample sizes required in various situations such
as estimation and hypothesis testing for both
variables and attributes as easy as possible.
The goals were minimizing the number of screens
a user had to go through before obtaining the
result, individual help screen for each prompt
with an example and reference and, finally. to
have the result appear on the same screen as the
prompts. These goals were all accomplished
using commands and options available in SAS/AF
software.
Examples of the programs and various screens and
problems encountered using SAS/AF software are
included.
3.
The system must contain plenty of on-line
help. In addition to the example situation,
additional explanation of all inputs required is given. References are also listed in
case further explanation is required.
4.
The programs must display the result on the
same screen as the input. This would avoid
confusion as to what input parameters
produced the result.
5.
A user of the program must view as few
screens as possible. For any application,
only two screens need to be viewed by the
user.
III. SAS/AF PROCEDURES
SYSTEM DEVELOPMENT
Developing the system involved five steps:
1. INTRODUCTION
Sample size calculations are frequently required
by engineers for applications such as process or
product qua.lification and experiment design. To
address this need, full-screen menu-driven
sample size calculation programs were written.
The programs were written using base SAS and
SAS/AF software.
II. SYSTEM REQUIREMENTS
The system was written so that engineers could
perform initial sample size calculations with a
minimum of assistance from a statistician. In
order for the system to fulfill this goal, the
following were felt to be requirements of the
system:
1.
The system must be menu-driven with few
screens. Menu-driven programs make the
system easy to use.
2.
The system must have examples of situations
where each calculation would be used. In
this way, the engineer can determine if the
option chosen is appropriate for their
situation.
1.
Writing and testing the sample size calculation programs independent of SAS/AF software
2.
Creating the SAS/AF menu and program screens
3.
Adjusting and testing the progreqs to interface with the screens
4.
Creating the help screens
5.
Putting the programs on common system disks
Step 1
The sample size calculation system was divided
into two categories, estimation and hypothesis
testing. Each of these groups was then further
divided into attribute data and variables data
for a total of thirteen different types of
calculations. Each type of sample size calculation represented a separate program.
The thirteen programs were first written in base
SAS software without using SAS/AF software.
Values for the variables that the user would
later input via the SAS/AF screens were contained
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within the programs. The program results would
be written to the SAS LOG. Each of the programs
was run several times modifying the variable
values and verifying the results in order to
test the sample size algorithms.
The ATTR command was entered from the command
line of MAIN.MENU next. This produced another
screen that allowed the programmer to specify
the program name that is to be executed depending on the selection the user makes, and which
PF Key and/or typed number would cause the
associated program to be executed.
Step 2
The program screens were then designed, each one
having the same format and colors.
The next step was to create the program selection
menu. The command:
A macro variable was used wherever the user is
to enter data-or program results displayed. Any
underscores that immediately follow a variable
name serve as place holders. For example, the
name &MSGS5 only takes up 6 bytes, but the field
it represents requires 7 bytes. The underscore
stands for the seventh byte.
PROC BUILD CATALOG-STAT .PGM; RUN;
was submitted from the,SAS display manager. The
BUILD procedure put the programmer into the
SAS/AF catalog where the actual menus and
program screens were developed.
The program screen for the estimation of a
normal standard deviation is shown below. It
was created in a manner similar to the main
menu. The command, EDIT VARO.PROGRAM, was
entered from the command line of the directory,
and the contents of the screen were then typed
in the blank screen area following the format
described above.
To create the main menu, EDIT MAIN.MENU was
typed on the command line.
The command DES Sample Size Calculations was
first entered onto the command line to change
the title of the screen. The default title that
originally showed up was MAIN.MENU, the menu
name.
The rest of the menu screen was simply typed in
the blank area exactly as it was to appear to
the user using the appropriate color keys. The
completed menu is shown below.
Sample Size Calculation
Command ==->
Text Editor
Col 001 079
Estimation of a Normal Standard Deviation
Problem Statement: The result will be the sample
size necessary to estimate S between sigma/f and
sigma*f, with about 100 (GAMMA) % probability.
Sample Size Calculations
Command ===>
ESTIMATION
Attribute Data
Please Input:
HYPOTHESIS TESTING
Attribute Data
f:
&fs5
GAMMA:
&gammas5
1. Binomial Proportions
8. Binomial Proportion,
one sample
2. Nonparametric Tolerance Intvls
9. Binomial Proportion,
two sample
Note: The accuracy of this approximation
increases with the sample sizes; it is reasonable for n > 15.
Variables Data
&m8g85_ &lmsgs5____________________ &ns5
Variables Data
3. Normal Mean, one
sample
10. Normal Mean, one
sample
4. Difference Between
Two Normal Means
11. Normal Mean, two
samples
5. Normal Standard
12. Normal Variance
Deviation
f
Text Editor
(Hit PFI for HELP, PF2 to SUBMIT, PF3 to EXIT.)
Next the ATTR command was executed from the
program screen in order to specify more information about each of the program variables.
The standard deviation program screen as the
user would see it is shown below. Underscores
automatically show up in place of the macro
variables &FS5 and &GAMMAS5 which signifies to
the user to enter data in these fields. The
other macro variables &MSGS5, &LMSGS5, and &NS5
do not show up at all, even as underlines, until
the program is submitted.
6. Normal Variance
(Based on C.I.
Midpoint)
7. Ratio of Two Normal
Variances
13. Ratio of Two Normal
Variances
(Hit PFI for HELP, PF3 to EXIT)
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Command ...
-->
Sample Size Calculation
Step 4
Estimation of a Normal Standard Deviation
The fourth step was to create the help screens.
Each help screen contained an example, and theformats and colors were similar. If the PF1 key
was hit from anywhere on the program screen, the
user would be shown an overall help screen. If
the cursor was positioned in one of the input
fields, a help specific to that variable would
be displayed.
Problem Statement: The result will be the sample
size necessary to estimate S between sigma/f and
sigma'f, with about 100 (GAMMA) % probability.
Please Input:
The overall help screen is shown below. The
help screens were created by issuing the EDIT
command. and then typing on the blank screen.
The overall help screen must have the same name
a8 the program. For example, the help screen
for VARO.PROGRAM was called VARO.HELP. The help
screens for each of the variables could have
been named anything as long as the second
qualifier was HELP and the name appeared on the
program screen attributes for the correct
variable.
f:
GAMMA:
Note: The accuracy of this approximation
increases with the sample sizes; it is
reasonable for n > 15.
(Hit PF1 for HELP, PF2 to SUBMIT, PF3 to EXIT.)
Est. of a Normal Standard Deviation
Command -==>
Press FORWARD for more.
PF2 to Exit Help Screen_
Step 3
Estimation of a Normal Standard Dev1ation~
sigma, between sisma/f and sigma*f, with 100
(GAMMA) % probability.
The next step involved copying the independent
programs and appending them onto their
associated SAS/AF program screens. The
programmer exited from the catalog returning to
the SAS display ~nager. In order to copy in
the Normal Standard Deviation Program, VARO SAS,
the following commands were executed:
Overall Help Screen
Example: We wish to estimate sigma (the standard
deviation of a normal distribution)
within a factor f-1.20 with 90%
probability. In this example, f - 1.20
and galDma - 0.90.
CMS FILEDEF VARO DISK VARO SAS A;
PROC BUILD CATALOG-STAT.PIlMS; RUN;
The programmer was then put back into SAS/AF
catalog, and the following commands were entered
one at a t:l.m.e:
Prompts:
1) f:
2) GAMMA:
EDIT VARO.PROGRAM
Common Values
any value greater than
0.90, 0.95, 0.99
FILL -
Reference: Nelson, W. (1982). tfApplied Life
Data Analysis." John Wiley and Sons,
New York.
INCLUDE VARO
Step 5
The EDIT command brought up the VARO program
screen that had been previously created. One
should note that the FILL command was issued
from the command line, but the cursor was moved
down to the end of the screen before the enter
key was hit. This caused a dashed line to be
put at the end of the program screen which
separates the screen from the program itself.
The INCLUDE command then appended the VARO SAS
program onto the end.
The final step was putting the programs' on
cammon system disks so the engineering community
would have access to the sample size system. A
small program, STATPGM EXEC, was written in
Restructured Extended Executor (REXX) language
and also put out on the system disks. This
makes it possible for an engineer to use the
system without knowing any SAS statements. From
Conversational MOnitor System (OMS). one needs
only to type the command, STATPGM. Within the
EXEC is:
Each of the programs written using base SAS
software was copied one by one in the same
fashion.
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IV. DEMONSTRATION
PROC DISPLAY CATALOG=STAT. PGMS .MAIN.MENU; RUN;
Example:
The exec also creates a log of all userlds using
the programs. This has been helpful to the
authors in measuring the system's usage.
Sample Size for Estimation of Mean
The following pages contain an example of
accessing and running the sample size programs.
The pr,ograms can be run by typing
In addition, the system does not use the default
PF keys that were installed at the site.
Therefore, the REXX program copies a 5PROFILE
SASUSER onto the user's disk. As soon as the
user exits from the sample size calculation
system, this profile is automatically erased.
One should note that before anything 1s copied
though, the program does check to see if the
engineer already has his own 5PROFILE SASUSER.
STATPGM
while in CMS. STATPGM is a REXX exec which
temporarily defines PF keys and displays the
Main Menu. In the example, option 10 is chosen.
This option is for calculating sample sizes for
hypothesis testing for a normal mean, one
sample. The input and help screens for this
example are shown.
If this is the case, the user 1s then informed
that his version will be renamed temporarily, or
he 1s given the chance to exit from the system.
Main Menu, Option 10 Chosen
HINTS/PROBLEMS
Sample Size Calculations
Color
Select Option
To use color in the screens was actually very
simple although this is not explained anywhere
in the SAS/AF manuals. If one is using an IBM
3279 model 3X, for example, the colors can be
changed by using the ALT key along with the PF
keys.
----->
10
Press END to return
ESTIMATION
HYPOTHESIS TESTING
Attribute Data
Attribute Data
1. Binomial Proportions
8. Binomial Proportion,
one sample
2. Nonparametric Tolerance Intvls
PF Keys
An inconsistency was found in the PF keys.
Variables Data
According to the SAS/AF documentation the END
and CANCEL commands should work from both help
screens and program screens.
From a program screen CANCEL will exit the
screen immediately, while END will submit the
program. Since most of the engineers at this
site are used to using PF3 as an exit key, the
PF3 key was set up to be CANCEL, and PF2 represented END.
9. Binomial Proportion,
two sample
Variables Data
3. Normal Mean, one
sample
10. Normal Mean, one
sample
4. Difference Between
Two Normal Means
11. Normal Mean, two
samples
5. Normal Standard
Deviation
12. Normal Variance
6. Normal Variance
(Based on C. I.
The help screens did not work like this though.
Entering the CANCEL command only produced an
error message. The only way to exit help was to
enter END. Therefore, the engineers must use
PF3 to exit from a program screen but PF2 to
exit from, a help screen.
Midpoint)
7. Ra tio of Two Normal
Variances
13. Ratio of Two Normal
Variances
(Hit PF1 for HELP, PF3 to EXIT)
Error Messages
Option 10 Input Screen
It is very easy to set up audits from the
Program Attribute Screen. When users input
invalid data, a message appears on the screen
automatically notifying them of an error. This
message is not very descriptive, however. It
will simply read "Invalid Entry at Row-XXX
Column-XXX. Please reenter." In this particular
system the valid entries are contained within
the help screens so it did not present a signif:", '
icant problem ..
Sample Size Calculations
Command
--->
Tests of Hypothesis About a Normal Mean
Problem Statement,: The result will be the sample
size necessary to test the hypothesis:
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Please Input:
HO: u - uO
where:
Standard Deviation:
DELTA - ABS(u - uO)
4.23
Delta:
Please Input:
Standard Deviation:
Alpha:
0.05
Delta:
Beta:
0.10
Alpha:
1-1 tailed, 2-2 tailed:
(Hit PFI for HELP, PF2 to SUBMIT, PrJ to EXIT.)
Beta:
1-1 tailed, 2-2 tailed:
Option 10 Input Screen With Final Sample Size
Result
(Hi t PFI for HELP, PF2 to SUBMIT, PF3 to EXIT.)
Sample Size Calculations
Help Screen for One- Versus Two- Tailed Test
Command
--=>
Tests of Hypothesis About a Normal Mean
Tests of Hypothesis About a Normal Mean
Command _••>
Press ~ to return.
Problem Statement-: The result will be the sample
size necessary to test the hypothesis:
PF2 to Exit Help Screen
One- Versus Two- Tails Help Screen
HO: u - uO
Example: We are producing parts that in the past
had a mean thickness of 30 angstroms
and a standard deviation of 3.7. After
introducing a change in the process, we
wish to determine if there has been
a decrease in mean thickness. In
par'ticular, if the thickness was as low
as 28 angstroms, we want to declare
this difference as significant. We
will choose alpha - 0.05 and beta 0.10. Please refer to the individual
help screen for alpha and beta for
interpretation of these values. In
this example, standard deviation· 3.7,
delta·· 2. and the test is one-tailed.
where:
Please Input:
Standard Deviation:
4.23
Delta:
Alpha:
0.05
Beta:
0.10
I-I tailed, 2-2 tailed:
RESULT:
Prompts:
DELTA - ABS(u - uO)
THE SAMPLE SIZE REQUIRED IS:
154
Common Values
(Hit PFI for HELP, PF2 to SUBMIT, PF3 to EXIT.)
1 - I-tailed. 2 = 2-tailed
1 or 2, here 1
Reference: Mace, A. E. (1964). "Sample Size
Determination." Reinhold Publishing
Corporation, New York.
1
®
®
SAS and sAS/AF are registered trademarks of
SAS Institute Inc., Cary, NC, USA.
Option 10 Input Screen, All Prompts Filled In
Sample Size Calculations
Command
References
==->
1.
Mace, A. E. (1964), Sample Size
Determination, Reinhold Publishing
Corporation, New York
2.
Nelson, W. (1982), Applied Life Data
Analysis. John Wiley and Sons, Inc. J New
York
3.
SAS/AF User's Guide. Version 5 Edition
(1985), sAS Institute, Inc., Cary, N.C.
Tests of Hypothesis About a 'Normal Mean
Problem Statement: The result will be the sample
size necessary to test the hypothesis:
HO:
where:
u -
uO
DELTA - ABS(u - uO)
1285