Project – Simulations in Excel
Objective: Use Excel for random number generation in order to answer
probabilistic questions.
Materials: You will need Microsoft Excel with the Analysis ToolPak installed.
Procedure: Here¹s how to do Random Number Generation in Excel.

Create a column of the possible digits (i.e. 0-9, or 00-99 or 000-999, etc.)

Put the associated probabilities of each digit in the column next to each
digit.
o
For example, if every digit is equally like and you have ten digits,
then each probability is 0.1. (If you had 100 digits, each probability
would be 0.01. )
o

Go to Tools  Data Analysis. (A pop-up window should appear.)
o
Scroll down to Random Number Generation. Click OK.
o
For Number Of Variables: 20


This is the number of simulations you want to perform.
If you wanted to do 100 simulations, you¹d put ³100² in this
box.
o
For Number Of Random: 30 (This would generate 30 random
#s)
 Here, you can always tell it how many random numbers you
want created
o
For Random Seed: Leave Blank
o
For Distribution: Discrete
 We¹ll work with some of the other distributions later
o
For Value and Probability Input: Click on A2 and drag to B11
 Obviously, if you were working with two digit or three digit
numbers, you¹d click and drag from the first possible digit
(upper left) to the last possible probability (lower right)
o
For Output Range: Click ³New Worksheet Ply² and name it
³Random Output²
 This will create a new worksheet that will display 20 columns
of 30 random digits.
o
The window below shows how to do 20 simulations of 30 random
digits and displays them in a new worksheet called ³Random
Output.²
o
SAMPLE Question:
Corinne is a 75% free throw shooter. In a particular game she had 12
attempts and made only 7. Simulate 50 trials of 12 shots. With what
probability did she make 7 or fewer baskets?

Column A = 00-99 (Use the ³Fill Down² <Control-D> feature to
quickly create the list of 100 numbers)
i. Let A2 be 00. Let A3 = SUM(A2, 1). Then do Fill Down.

Assign 00-74 to ³make² and 75-99 to ³miss²

Column B = 0.01. Use Fill Down again.

Use the RNG to create 50 sets of 12 random numbers on a new
worksheet.

For each column, you need to figure out if she made fewer than 7
baskets.
i. Use this in A14: =CountIF(A1..A12, ³<75²)
1. Note: could also use: =CountIF(A1..A12, "<=74")
ii. Use the Fill Right <Control-R> command to calculate for all 50
simulations.
iii. Then, in A15, use this: =IF(A14 < 8, 1, 0)
1. This will become a ³1² if she made fewer than 7
baskets and a ³0² if she made seven or more.
2. Note: could also use: =IF(A14 <= 7, 1, 0)
iv. Use the Fill Right command to calculate for all 50
simulations.
v. To calculate the probability, just take the sum of everybody in
row 15 and divide by 50. This will give you the experimental
probability she made less than 7 baskets. For example, you
could let A17 = SUM(A15..A64)/50

Conclusion: Does it seem like Corinne choked? Why or why not?
YOUR PROJECT:

Elaine is enrolled in a self-paced course that allows three attempts at
passing an examination on the material. She does not study and has only
a 2 out of 10 chance of passing.
o Mathematically, what is Elaine¹s probability of passing at least one
of the three attempts? (You may assume the attempts are
independent since the exam is different each time.)
o Simulate 50 repetitions. What is your estimate of Elaine¹s
likelihood of passing the course based on your simulation?
A more realistic model for Elaine is as follows: She has a 20% chance of
passing the first exam, a 30% chance the second time around, and a 40%
chance the third time around. She will, of course, stop taking the test as soon
as she passes but she is only allowed at most three attempts at the test.
o
o
Explain how to simulate one repetition of Elaine¹s tries at the
exam.
Simulate 50 repetitions and estimate the probability Elaine
eventually passes the exam.