1
Overview
In this lesson, students use coin flip results to take a simultaneous random walk on a number
line. Using their own motions as a probability simulation, students investigate, develop, and
analyze a probability model for compound events.
Prerequisite Knowledge
Students should be familiar with finding probabilities of events like coin flips. Students should
also have experience with plotting numerical data in plots on a number line or histogram.
Lesson Goals for Grade 7
Students will:
• use a simulation to generate frequencies for compound events
• draw conclusions about probability models by examining frequencies in data
• find probabilities of compound events by creating representations of sample spaces
• use a probability distribution to generate and answer questions about probability
Lesson Day 1
Overview
A student takes a random walk on a number line determined by flips of a fair coin: one step
forward with a flip of a heads, and one step back with a flip of tails. After students propose
questions about an individual’s random walk, the whole class, joined by other students if
possible, conducts a simultaneous random walk. Students arrive in various locations on the
number line and then walk into columns to create a human bar graph that records their final
location. Students then investigate the theoretical probabilities involved in the random walk.
Introduction (5-10 minutes):
We’re going to go for a walk today. But it’s going to be a funny kind of walk… we’re going to let
coin flips be your guide.
Select a volunteer walker and another student to flip a coin. With the walker standing in a
suitable location, explain to the class that the student will take one step forward when the coin
lands heads, and one step back when the coin lands tails. With each flip, have the volunteer
take a step forward or back. Repeat 6-10 times to interest students in the randomness of the
student’s motion.
If you were feeling random one day, and were to take a walk with coin flips as your guide like
our volunteer just did, what would you wonder about? What would you be curious about?
Record your thoughts on the handout. (Distribute the “Flip Trip” handout.) Allow students
time to generate questions; circulate to see what students are writing.
As you distribute coins, ask students to share their thoughts. Possible responses:
How often will I get heads or tails?
Where will I arrive after a certain number of flips?
How long will it take me to get to the other end of the room?
What are my chances of getting to the other end of the room?
It would take forever just to walk a couple of feet!