COM 508
PSC 508
Assignment 3


ZforB is a program that lets you see the similarities and
dissimilarities between the normal distribution and the binomial
distribution.  On the web site are two files:  ZforB.exe and
ZforB.bas.  The former file is the executable program file, and the
latter is the QuickBasic code that I used to create the executable.

1. Download the executable.  You may download and explore the code
file if you wish, but you will definitely need the executable.


2. Play with the program a while.  It is a DOS program, so you will
either need to boot up with DOS or run the program from a DOS window.
Try different settings for the number of marbles dropped and the
probability of success.  Set p equal to .5, close to .5, or far from
.5 (e.g., something like .95 or .03).  Drop a large number of
marbles; drop a small number of marbles.  Try different delays.


3. After getting comfortable with the program, I want you to use the
program to create 3 data files.  I will let you pick the
probabilities provided they meet the following constraints:  One file
should be for a combination of N and p that gives a product of N(p) <
5; one should have N(1-p) < 5; and one should have them both exceed
5.  Remember, in ZforB, N is set for 20 (there are 20 rows of nails),
so you will have to manipulate the products by choosing various
probabilities.  Anyway, for each data file, use SPSS to create a
normal probability plot (P-P plot) and a histogram with the normal
curve superimposed.  Label your output (by hand is ok) with the
particular values of p that you used.

4. Answer the following question:  In what situation is the normal
approximation to the binomial most appropriate?

5.  Hand in your output, your syntax, and your answer to the
question.