Each group needs:

• two clear cups
• random selection tool, such as a bag with colored pieces of paper; students draw one piece randomly from the bag when they need to choose a random color
• 20 pom poms, created from yarn, or an equivalent item that can be used for counting (these items do not need to be unique to every group);

To share with the entire class:

• ball (soft like a tennis ball)
• strings of yarn
• pipe cleaners for arrow heads, shown below in Figure 1 (optional)