Probability Lab Guide
Lab Instructor Guide
Compound Event Quest • Intervention Unit
Target Standard
CO 7.SP.C.8: Compound Probability
Group Size
Small Group (3-5 Students)
Duration
45 - 60 Minutes
Intervention Strategy: The CRA Model
Concrete
Flipping coins and rolling dice to physically generate data points.
Representational
Organizing results into tree diagrams and tables to visualize the sample space.
Abstract
Calculating P(event) by dividing desired outcomes by total outcomes in the sample space.
Delivery Sequence
1
The Discovery Flip (10 mins)
Start with a single coin flip. Ask: "What can happen?" Then, introduce a second coin. Ask: "If I flip both, how many different ways can they land?"
Probing Question: "Is 'Heads, then Tails' the same as 'Tails, then Heads' when we look at the total outcomes? Why or why not?"
2
Visual Blueprinting (15 mins)
Demonstrate the Tree Diagram. Use one branch for Event A (Coin) and sub-branches for Event B (Dice). Transition to the Table Method to show how they represent the same information.
Scaffold: Color-coding Scaffold: Pre-drawn roots
3
The Simulation Lab (20 mins)
Students use physical tools (1 coin, 1 die) to perform 24 trials. They record results in their packet and compare their experimental results to the theoretical sample space they built.
Diagnostic & Intervention Support
Common Misconceptions
Addition vs. Multiplication
Students may add the number of outcomes (2 + 6 = 8) instead of multiplying them (2 × 6 = 12) to find the total sample space size.
Ignoring Order
In two-coin flips, students often think {H, T} and {T, H} are the same outcome, leading to a sample space size of 3 instead of 4.
Correction Strategies
The "Path" Technique
Have students trace a finger from the root of a tree diagram to the tip of a branch. Each full path = 1 unique outcome.
Grid Verification
Use a table to show that every row/column intersection MUST have an outcome. Count the boxes together.
Small Group Discussion Prompts
-
"If we added a third event, like picking a color, how would our tree diagram change? Would it get taller or wider?"
-
"In our simulation, did anyone get 'Heads and 6' exactly 1/12th of the time? Why is the simulation result usually slightly different from the math?"
-
"Which tool felt easier to use for finding all the outcomes: the table or the tree? Why?"
Lab Station Checklist
1 Standard Coin per student
1 Six-sided Die per student
Student Event Explorer Packets
Highlighters (2 colors)
Probability Lab Slides
PROBABILITY LAB
The Compound Event Quest
What is a Compound Event?
Simple Event
ONE thing happens.
Flip 1 Coin
Compound Event
TWO OR MORE things happen together.
Flip 1 Coin AND Roll 1 Die
Mapping the Path
The Tree Method
A Tree Diagram helps us see every possible path from start to finish.
1
Draw branches for the 1st event.
2
Draw sub-branches for the 2nd event.
3
Follow the paths to find all outcomes!
START
HEADS
TAILS
1, 2, 3, 4, 5, 6
1, 2, 3, 4, 5, 6
The Power of the Grid
| 1 | 2 | 3 | ... |
|---|
| Heads | H, 1 | H, 2 | H, 3 | ... |
| Tails | T, 1 | T, 2 | T, 3 | ... |
Total Outcomes = 2 (Coin) × 6 (Die) = 12
Simulation Lab Time!
Step 1: Predict
Before flipping, guess how many times you will get "Heads and a 5".
Step 2: Trial
Perform 24 trials. Record every flip and every roll in your lab packet.
Step 3: Analyze
Compare your results to the sample space we built. Were they close?
