Decision Trees 101

Mapping Your Choices

60 Minute Session

Session Objectives

By the end of this lesson, students will:

  • Understand what decision trees are and how they help in decision-making.
  • Learn to identify decisions, alternatives, probabilities, and outcomes.
  • Practice creating simple decision trees based on everyday scenarios.
  • Recognize the value of structuring problems to make better decisions.

Making Choices: The First Step to Better Decisions

Time: 10 minutes

Think back to this morning, or maybe yesterday. Can you remember a time when you had to make a choice between two or more options? Maybe you were deciding what to wear, what to eat, or whether to start your homework right after school or take a break first.

Let me share an example: Yesterday, I had to decide whether to walk to the store or wait for a ride. If I walked, I could go right away, but it would take longer and I might get tired. If I waited for a ride, it would be faster and easier, but I wasn’t sure when the ride would be available. Each choice had good points and not-so-good points.

Now it’s your turn. Tell me about a choice you had to make recently:

  • What were your options?
  • What made the decision tricky?
  • How did you finally decide what to do?
  • Looking back, are you happy with your choice?
making-better-decisions

You know what’s interesting about the decision you just described? There were probably several things you thought about before making your choice. Maybe you considered:

  • How much time you had
  • What else you needed to do that day
  • What other people might think or feel about your choice
  • What could go right or wrong with each option

Today, I’m going to show you a really cool tool called a decision tree. It’s like drawing a map of your choices, and it can help you see all your options clearly. Just like a real tree has branches that spread out in different directions, a decision tree shows all the different paths your choice could take.

Sometimes when we have to make a choice, it feels like all our options are jumbled up in our head. A decision tree helps us lay everything out clearly so we can make better choices. Would you like to learn how to make one?

Teaching Note: This warm-up helps students recognize that they’re already making decisions constantly and thinking through options, even if they don’t do it systematically. It prepares them to see how decision trees can make this natural process more organized and effective.

The Martinez and Thompson Story: A Tale of Two Neighbors

Time: 15 minutes

Let me tell you a story about two families who lived next door to each other – the Martinez family and the Thompson family. For years, they were great neighbors. Their kids played together, they shared backyard barbecues, and they helped each other out whenever needed.

But then something happened that changed everything. One day, the Martinez family’s dog accidentally dug up Mrs. Thompson’s prized garden. Mrs. Thompson was really upset, and instead of talking it out, both families got angry. They stopped speaking to each other. Their kids couldn’t play together anymore. When they saw each other, they would make angry faces or say unkind things.

This went on for months. Both families were unhappy, and it affected everyone around them too. Their other neighbors felt uncomfortable, and the neighborhood wasn’t as friendly anymore.

Let’s draw out what we call a decision tree to see what choices these families had.

Neighbor Conflict Stay Angry Unhappy Separated Worse Try Peace Friends Kids Play Happy No Worse Try Again Decision Good Outcome Bad Outcome

The main decision point was this: Should they continue being angry at each other, or should they try to make peace?

If they continued being angry:

  • They would stay unhappy
  • Their kids would stay separated
  • The neighborhood would remain uncomfortable
  • Things might get even worse

If they tried to make peace:

  • They might become friends again
  • Their kids could play together
  • The neighborhood would be happier
  • Even if it didn’t work perfectly, they wouldn’t be worse off than before

Here’s what’s interesting: when we draw it out like this, we can see that trying to make peace was probably the better choice. Even if it didn’t work out perfectly, they wouldn’t lose anything by trying. But if it did work, everyone would benefit.

What do you think? If you were part of one of these families, what would you choose? Why?

Let’s think about what happened next. The Martinez family’s daughter, Sofia, and the Thompson family’s son, Tyler, both missed playing together. One day, Sofia decided to write an apology note about their dog and included some seeds to help replant the garden. The Thompson family was touched by this gesture, and Mrs. Thompson brought over some cookies in return.

This simple decision – choosing to take a step toward peace instead of staying angry – changed everything. The families started talking again, the garden was replanted together, and the neighborhood became friendly once more.

Teaching Note: This adapted story maintains the core lesson about decision consequences while being more relatable to young students. The decision tree visual helps students see how mapping out choices can lead to better decisions.

Understanding Decision Trees: A Map for Your Choices

Time: 10 minutes

You know how we use maps to find our way to new places? Well, a decision tree is like a map for your choices. It helps you see all the different paths you could take and where they might lead.

Let me show you how it works. Imagine you’re standing at the start of your decision, just like you’re standing at the beginning of a path. In front of you, the path splits into different directions – these are your choices. Each direction you could take might lead to different outcomes, just like different paths might lead to different destinations.

Let’s break down the parts of a decision tree:

First, we have what we call “Decision Nodes.” We draw these as little squares ⬛. This is where you make a choice, like choosing between doing homework now or later.

Then we have “Chance Nodes,” which we draw as circles ⭕. These show places where something might or might not happen – like whether it will rain during your soccer game.

The lines connecting these shapes are called “branches.” They show all the different ways things could go. Think of them like the different paths you could take.

At the end of each branch, we write what might happen – we call these the “outcomes.” These are like the destinations on your map.

Let’s try a simple example: Should you study for tomorrow’s test?

⬛ Study for test?
├── Yes
│ ├── ⭕ Test Result
│ │ ├── Good grade (likely)
│ │ └── Average grade (less likely)

├── No
│ ├── ⭕ Test Result
│ │ ├── Good grade (unlikely)
│ │ └── Poor grade (likely)

Study for test? Yes No Test Test Good grade (likely) Average grade (less likely) Good grade (unlikely) Poor grade (likely) Decision Node Chance Node Likely Good Outcome

See how this helps us think through what might happen? When we draw it out like this, it’s easier to see which choice gives us the best chance of a good outcome.

The really cool thing about decision trees is that they can help with all sorts of choices, from simple ones like what to wear to bigger ones like which after-school activities to join.

What’s a decision you’re thinking about right now? Should we try drawing a tree for it?

Teaching Note: Keep the initial examples simple and relatable. The goal is to help students see decision trees as a helpful tool rather than a complicated process.

Drawing Out Your Choice: Play or Soccer?

Time: 15 minutes

Let’s create a decision tree together for a choice many students face: choosing between different after-school activities. Imagine you need to decide between joining the school play or the soccer team. Both sound fun, but you only have time for one.

First, let’s start with our decision node – we’ll draw a square ⬛ and write “Which Activity?” next to it.

Now, let’s draw two branches coming out from this square – one for “Join School Play” and one for “Join Soccer Team.”

At the end of each branch, we’ll draw circles ⭕ because we’re not sure exactly what will happen – there’s an element of chance involved.

Let’s think about what might happen if you choose the play:

  • You might discover you love acting and make great friends
  • You could get a big part or a small part
  • Rehearsals might conflict with other activities
  • You might get stage fright
  • The play could be really successful
  • You’ll learn new skills like public speaking

And what about choosing soccer:

  • You could become a better player
  • You might make new friends who love sports
  • There’s a chance of getting injured
  • You might not get much playing time
  • The team could win lots of games
  • You’ll get stronger and fitter

Let’s add all these possibilities to our tree.  Your tree might look something like this:

⬛ Which Activity?
├── Join School Play
│ ├── ⭕ Possible Outcomes
│ │ ├── Get lead role
│ │ │ ├── Love performing
│ │ │ └── Get nervous
│ │ └── Get small role
│ │ ├── Enjoy being part of show
│ │ └── Feel disappointed
└── Join Soccer Team
├── ⭕ Possible Outcomes
│ ├── Make starting team
│ │ ├── Win games
│ │ └── Lose games
│ └── Be substitute
│ ├── Improve with practice
│ └── Feel frustrated

Now, looking at this tree, let’s think:

  1. Which outcomes seem most important to you?
  2. Which risks worry you more?
  3. What other branches should we add?
  4. How does seeing all these possibilities help you decide?

Remember, the goal of making a decision tree isn’t just to pick the “right” choice – it’s to help you think through your options carefully and understand what matters most to you.

Teaching Note: Encourage students to add their own branches and outcomes. The more personally relevant they make the tree, the better they’ll understand how to use this tool for their own decisions.

Sharing Our Decision Trees

Time: 10 minutes

Now that you’ve created your own decision tree, let’s explore it together. This is your chance to explain your thinking and maybe discover some possibilities you hadn’t considered.

Tell me about your decision tree:

  • What choice were you trying to figure out?
  • Walk me through each branch – what could happen in each case?
  • Which outcomes do you think are most likely?
  • Were there any surprises when you drew it all out?

I’ll share some ideas that might add to your tree:

  • Have you thought about…? (suggest an outcome they might have missed)
  • What if this happened…? (propose an unexpected possibility)
  • How would you handle this situation…? (explore a challenging outcome)

Let’s think about how someone else might draw this same decision tree:

  • What might your best friend put as outcomes?
  • What would your parents consider important?
  • Are there other viewpoints we should consider?

The great thing about sharing decision trees is that we often discover new possibilities we hadn’t thought of before. Sometimes other people can see things we might miss.

What’s the most helpful thing you learned from drawing out your decision this way?

Teaching Note: In a small group setting, have each student share their tree while others contribute additional branches or outcomes they might consider. For one-on-one instruction, take turns sharing examples and building on each other’s ideas.

Looking Back: How Decision Trees Help Us

Time: 5 minutes

Let’s take a few moments to think about what we’ve learned today about decision trees and how they can help us make better choices.

Take out your journal. We’ve learned a new tool today – the decision tree – that can help us when we’re facing tricky choices. Think about:

  1. When might drawing out a decision tree be most helpful to you?
  2. What surprised you about mapping out decisions this way?

Write your thoughts in your journal, starting with:
A decision tree could help me when...”

For example, you might write:
I could use a decision tree next time I need to decide how to spend my weekend. It would help me see all my options and think about what might happen with each choice.

Or:
Drawing out my choices could help me when I’m not sure about joining a new activity. I can map out the good and not-so-good things that might happen.

Would you like to share what you wrote? What did you learn today that you think will be most useful in your life?

Teaching Note: This reflection helps students internalize the concept of decision trees and think about practical applications in their own lives.

Wrapping Up Our Decision Tree Adventure

Today you learned a powerful tool for making better choices – the decision tree. Just like a real tree has branches spreading out in different directions, your decision tree helps you see all the different paths your choices might take.

Remember our story about the Martinez and Thompson families? When they drew out their choices like a tree, they could see that trying to make peace was worth the risk. Sometimes just seeing all our options clearly helps us make better decisions.

 

Your Decision Tree Challenge

For the next few days, try using decision trees at home with your family. Pick something you need to decide together, like:

  • Planning a weekend activity
  • Choosing what to have for a special dinner
  • Deciding on a new family rule
  • Picking a movie to watch together

Draw out your decision tree showing all the possible choices and what might happen with each one. You might be surprised at what you discover when you map it all out!

When we meet next time, we’ll learn something really cool – how to add probabilities to our decision trees. This will help us figure out which paths are more likely to happen. Bring your family decision tree to share – I’d love to see how you used this tool at home.

Remember: A decision tree isn’t about finding one perfect answer. It’s about seeing all your options clearly so you can make choices you feel good about. What was your favorite part about learning to make decision trees? What kind of decisions do you think you’ll map out next?

For Parents/Teachers:

The student should now understand the basic structure of decision trees and be able to create simple ones for everyday decisions. They should see this as a helpful tool rather than a complicated process.

Song: Map your Choices

Verse 1:
Draw a square, that’s where you start
When choices pull your mind apart
Then draw your branches left and right
Like paths that lead to day and night
Each branch a different way to go
Each path with things you need to know

Chorus:
Map your choices like a tree
Draw the paths for all to see
Some lead here and some lead there
But when you draw them out with care
The way ahead gets clear and bright
Like holding up a guiding light

Verse 2:
Circles show what might occur
When chance makes everything a blur
At every end write what could be
The outcomes that you hope to see
Just like our neighbors learned to show
Sometimes you’ve got to map to know

(Chorus)

Bridge:
Better choices start to show
When you take the time to draw
All the paths where you could go
And what each choice has in store

(Chorus)

Outro:
So when choices make you pause
Draw them out and you will see
Every path has its own cause
In your decision tree