Hands-on Activity: Rock, Paper, Scissors Probability!
Educational Standards :
Pre-Req Knowledge (Return to Contents)
Ability to perform division and an understanding of the concept of ratios and the basic concept of probability and possible outcomes given certain scenarios.
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
Each group needs:
To share with the class:
Note that single licenses and site licenses are available; site licenses may make sense for schools with high use.
Introduction/Motivation (Return to Contents)
(Quarter Flip Demo: In front of the class, flip a quarter to demonstrate the probability of a quarter landing on heads vs. tails.)
What is the probability that this quarter will land on tails if I flip the quarter 10 times?
(Write the following on the classroom board: 2 green marbles, 3 yellow marbles and 4 blue marbles.)
What is the probability of picking a blue marble if you put all these marbles in a bag and draw from the bag? (Answer: In ratio form, 4/9.)
In order to understand probability, we need to understand what is meant by this word. Probability is defined as a chance that an event will occur. We can mathematically represent probability in equation form. (Write Equation 1 on the board).
Probability is simply a ratio between desired outcome and total outcome. In other words, the desired outcome can never be greater than the total outcome. If the rock-paper-scissors (RPS) robot is asked, "What is the probability of the robot throwing a rock?", the desired outcome is rock, which is 1 since only one rock is present, and the total outcome is 3, since rock, paper and scissors are present. Therefore, the probability of the robot throwing a rock can also be stated in equation form. (Write Equation 2 on the board.)
To make this activity fun for you, we have programmed a LEGO MINDSTORMS NXT robot (see Figure 1) to help you collect data and learn about probability. We'll call it the RPS robot, to represent rock-paper-scissors.
By using the RPS robot, we can associate probability to an event that is random. Just as in real life, probability occurs in a random manner (car accidents, building collapses, death, etc.); the outcome of the RPS robot is also random since a random number is generated by the robot. Also in keeping with real life in which random events cannot be known for certainty, the RPS robot's output (whether it throws rock, paper or scissors) cannot be determined either—it can only be guessed. Let's get started learning about probability!
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Before the Activity
The RPS Robot
This activity is centered around the NXT RPS robot (see Figure 2); so it is important to demonstrate to students the components of the robot and the mechanics of how the robot functions.
Download and execute the NXT program "rock_paper_scissors.rbt" and go through a few trial runs of the RPS game simulation.
Demonstrate to students how the RPS robot functions by introducing its components, as shown in Figure 3. Each component (the rock, paper and scissors) is attached to a motor, and a touch sensor controls when to "throw." For example, "rock" is represented by a LEGO NXT wheel. The touch sensor located on the side of the LEGO robot (see Figure 2) controls the output of the robot.
Once the touch sensor is pressed, the robot generates a random number, one, two or three, and assigns this to one of the motors. Depending on which motor is randomly chosen, the resulting output is the corresponding rock, paper or scissors object.
Press the touch sensor once; then, after the robot "throws" an outcome, the motor returns to its default position as shown in Figure 3. You can keep repeating this procedure until the program is manually terminated or the battery is unplugged. Demonstrating this action in front of class helps students to visually notice what is happening once the touch sensor is pressed.
Point out to students that there is no way to guess the future outcome, since all of the outcomes are based on random numbers.
With the Students
Attachments (Return to Contents)
Assessment (Return to Contents)
Pre-Quiz: Have students complete the five-question Pre-Assessment Quiz to gauge their base understanding of the subject of probability.
Activity Embedded Assessment
Worksheet: Have students complete their own RPS Worksheets while working in their teams. During the activity, monitor students' progress on the worksheet sections. At the end of class, collect the worksheets and evaluate students on their mastery of the subject of probability.
Post-Quiz: Administer the five-question Post-Assessment Quiz (nearly the same as the pre-quiz) and review students' answers compared to their pre-lesson answers to measure their comprehension of the subject of probability. Alternatively, as a class ask and discuss the quiz questions.
ContributorsAkim Faisal, Janet Yowell
Copyright© 2013 by Regents of the University of Colorado; original © 2011 Polytechnic Institute of New York University
Supporting Program (Return to Contents)AMPS GK-12 Program, Polytechnic Institute of New York University
Acknowledgements (Return to Contents)
This activity was developed by the Applying Mechatronics to Promote Science (AMPS) Program funded by National Science Foundation GK-12 grant no. 0741714. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.
Additional support was provided by the Central Brooklyn STEM Initiative (CBSI), funded by six philanthropic organizations.