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Experimental Probability and Relative FrequencyActivities & Teaching Strategies

Active learning works for experimental probability because students need to experience chance directly. When they flip coins or roll dice themselves, they see firsthand how probabilities emerge from repetition, making abstract concepts concrete. This hands-on approach builds intuition and reveals why chance behaves the way it does.

Grade 9Mathematics4 activities30 min45 min

Learning Objectives

  1. 1Calculate the experimental probability of an event based on collected data from trials.
  2. 2Compare experimental probabilities with theoretical probabilities for a given event.
  3. 3Analyze the relationship between the number of trials and the accuracy of experimental probability.
  4. 4Design and conduct a simple experiment to determine the experimental probability of a specific outcome.
  5. 5Explain discrepancies between experimental and theoretical probabilities using concepts of randomness and sample size.

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45 min·Whole Class

Whole Class: Coin Flip Marathon

Have the whole class flip coins simultaneously for 10, 50, and 100 trials per student, recording heads in a shared spreadsheet. Calculate relative frequencies after each round and plot on a class graph. Discuss how results change with more trials.

Prepare & details

Compare experimental probability to theoretical probability, explaining potential discrepancies.

Facilitation Tip: During the Coin Flip Marathon, circulate to ensure groups record results accurately and use consistent counting methods.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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35 min·Small Groups

Small Groups: Dice Probability Relay

Groups roll a die 200 times total, passing it relay-style, and tally outcomes on a group chart. Compute experimental probabilities for each face and compare to theoretical 1/6. Predict outcomes for fewer trials and test.

Prepare & details

Analyze how the number of trials affects the convergence of experimental probability to theoretical probability.

Facilitation Tip: For the Dice Probability Relay, place a timer at each station and have students rotate quickly to keep energy high.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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40 min·Pairs

Pairs: Custom Spinner Design

Pairs create spinners divided into unequal sections, spin 100 times, and record data. Calculate probabilities, then swap spinners with another pair to verify. Graph results to show convergence.

Prepare & details

Construct a simple experiment to determine the experimental probability of an event.

Facilitation Tip: In the Custom Spinner Design activity, provide protractors and colored pencils so students can precisely label their spinners.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

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30 min·Individual

Individual: Marble Jar Simulation

Each student draws marbles from a jar with known ratios 50 times with replacement, tracking frequencies. Calculate probabilities and reflect on discrepancies in a journal entry.

Prepare & details

Compare experimental probability to theoretical probability, explaining potential discrepancies.

Facilitation Tip: During the Marble Jar Simulation, give each pair a sealed container so they cannot peek and change their sampling method.

Setup: Varies; may include outdoor space, lab, or community setting

Materials: Experience setup materials, Reflection journal with prompts, Observation worksheet, Connection-to-content framework

ApplyAnalyzeEvaluateSelf-AwarenessSelf-ManagementSocial Awareness

Teaching This Topic

Teach this topic by letting students run experiments before defining terms. Start with a few trials to show unpredictability, then scale up to hundreds to reveal patterns. Avoid lectures on probability formulas early on. Instead, let students discover the law of large numbers through their own data. Research shows this approach builds durable understanding better than abstract explanations alone.

What to Expect

Successful learning looks like students connecting their observations to probability language. They should fluently calculate both experimental and theoretical probabilities, explain variability in results, and recognize when sample sizes matter. Most importantly, they should use evidence from their experiments to discuss reliability and chance.

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Watch Out for These Misconceptions

Common MisconceptionDuring the Coin Flip Marathon, watch for students assuming that after 10 flips with 6 heads, the next flip is more likely to be tails.

What to Teach Instead

Use the pooled class data to show how the proportion of heads stabilizes around 0.5, and ask students to explain why the law of large numbers makes individual flips unpredictable.

Common MisconceptionDuring the Dice Probability Relay, listen for students believing that a small number of rolls (e.g., 20) gives a reliable estimate of the probability of rolling a 4.

What to Teach Instead

Ask students to graph their results on a line plot and discuss how the graph flattens out as trials increase, making variability more visible.

Common MisconceptionDuring the Custom Spinner Design, notice students thinking that a section's size affects the outcome of the next spin.

What to Teach Instead

Have students spin their spinners 50 times and compare the experimental probability to the theoretical value, then ask them to reflect on why the spinner has no memory.

Assessment Ideas

Quick Check

After the Dice Probability Relay, present students with a scenario: 'A die was rolled 50 times, and the number 3 appeared 12 times.' Ask them to calculate the experimental probability of rolling a 3 and the theoretical probability. Then, have them explain any difference using language from the activity.

Exit Ticket

During the Marble Jar Simulation, give students a bag with 5 red marbles and 5 blue marbles. Ask them to state the theoretical probability of drawing a red marble, describe the experiment they conducted to find the experimental probability, and predict how the experimental probability might change if they drew 100 times instead of 10.

Discussion Prompt

After the Coin Flip Marathon, facilitate a class discussion using the prompt: 'Imagine you flip a coin 10 times and get heads 7 times. Is this result surprising? Why or why not? How would your confidence in the coin being fair change if you flipped it 1000 times and got heads 700 times?'

Extensions & Scaffolding

  • Challenge: Ask students to design a spinner with three unequal sections and predict how many spins are needed to match the theoretical probability within 5%.
  • Scaffolding: Provide a pre-labeled table for the Marble Jar Simulation with columns for trial number, outcome, and running total.
  • Deeper exploration: Have students research real-world applications of relative frequency, such as weather forecasting or sports analytics, and present how probabilities are used in those fields.

Key Vocabulary

Experimental ProbabilityThe ratio of the number of times an event occurs to the total number of trials conducted in an experiment. It is often expressed as a fraction or decimal.
Relative FrequencyAnother term for experimental probability, representing how often an event occurred relative to the total number of observations.
Theoretical ProbabilityThe ratio of the number of favorable outcomes to the total number of possible outcomes in a sample space, calculated without conducting an experiment.
TrialA single performance of an experiment or a single observation of an event, such as flipping a coin once or rolling a die once.
Sample SpaceThe set of all possible outcomes of an experiment or random process.

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