Compound Events & Trees
📋 What it is
A tree diagram maps every branch of a multi-step event, making outcomes easy to count.
🗣️ Coach says
A tree diagram organises a compound event: each step is a set of branches, and each full path is one outcome. Trees stop you from missing or double-counting possibilities — perfect for two or three stages.
🧠 Memory hook
One branch per choice; one full path = one outcome. Multiply along a path for its probability.
😂 Giggle
What's a statistician's favorite ride at the amusement park?
The roller-coaster — it has the best standard deviations!
😲 Whoa!
Tree diagrams aren't just for maths — they power decision-making in medicine, chess engines and "choose your own adventure" stories.
✅ Quick check: A tree for two coin flips has how many complete paths (outcomes)?
Say your answer out loud first — then reveal.
4 — two branches at flip one, each splitting into two at flip two.
Each stage multiplies the branches: 2 × 2 = 4 full paths.
🧪 Try it! (2 minutes)
Draw a tree for choosing a shirt (2 colours) then a hat (2 colours). Count the outfits.