Branches of a Probability Tree

In the picture

1. 1Badge 1 sits on the head of the left brass peg, the single starting point every ribbon leaves from.
2. 2Badge 2 sits on the copper tag clipped to the upper first ribbon, which carries that branch’s chance of 1/2.
3. 3Badge 3 sits on the head of the smaller peg where the upper ribbon splits a second time.
4. 4Badge 4 sits on the top ivory card with two black discs, one finished outcome at the end of a path.

Examples

• Flip a coin twice: each of the four paths is 1/2 x 1/2 = 1/4.
• Two traffic lights on the way home: green then red is one path through the tree.

Quiz: Branches of a Probability Tree (Age 18)

1. 1

   On a probability tree, how do you work out the chance of the outcome sitting at the end of a path?

   • Add the chances on the branches along that path
   • Multiply the chances on the branches along that path
   • Take the largest chance among the branches along that path
2. 2

   What does the fraction written on a single branch of a probability tree tell you?

   • The chance of that one step alone, once you have reached the point the branch starts from
   • The chance of the whole path that the branch belongs to
   • How many outcomes are still left further along the tree
3. 3

   A path leaves the starting point on a branch marked 1/2, then carries on along a branch marked 1/3. What is the chance of the outcome at the end of that path?

   • 1/6
   • 1/3
   • 5/6

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.